[overleaf-editor-core] Restructure TextOperation hierachy (#16582)

* [overleaf-editor-core] Restructure TextOperation hierachy

Restructures the hierachy of TextOperations to include a superclass
EditOperation. This superclass will later on contain other classes used
for tracked changes and comments.

* [overleaf-editor-core] Update json format of LazyStringFileData

* [history-v1+project-history] Fix TextOperation.fromJSON calls

* [overleaf-editor-core] Change EditOperationBuilder.fromRaw to fromJSON

* [overleaf-editor-core] Update apply and invert functions to accept FileData

* [overleaf-editor-core] Pass missing argument to store method

* [overleaf-editor-core] Remove unused method

* [overleaf-editor-core] User EditOperationTransformer

* [overleaf-editor-core] Clean up JSDoc comments

* [overleaf-editor-core] Add tests for EditOperation

* [overleaf-editor-core] Update JSDoc types

GitOrigin-RevId: 9c22a3a89b8483bdb87b43f329ddbdd887ffed42

libraries/overleaf-editor-core/index.js

@@ -20,6 +20,7 @@ exports.RestoreOrigin = require('./lib/origin/restore_origin')
 exports.Origin = require('./lib/origin')
 exports.OtClient = require('./lib/ot_client')
 exports.TextOperation = require('./lib/operation/text_operation')
+exports.EditOperation = require('./lib/operation/edit_operation')
 exports.safePathname = require('./lib/safe_pathname')
 exports.Snapshot = require('./lib/snapshot')
 exports.util = require('./lib/util')

libraries/overleaf-editor-core/lib/file_data/hollow_string_file_data.js

@@ -1,5 +1,9 @@
+// @ts-check
 'use strict'
 
+/**
+ * @typedef {import('../operation/edit_operation')} EditOperation
+ */
 const assert = require('check-types').assert
 
 const FileData = require('./')
@@ -44,9 +48,12 @@ class HollowStringFileData extends FileData {
     return this
   }
 
-  /** @inheritdoc */
-  edit(textOperation) {
-    this.stringLength = textOperation.applyToLength(this.stringLength)
+  /**
+   * @inheritdoc
+   * @param {EditOperation} operation
+   */
+  edit(operation) {
+    this.stringLength = operation.applyToLength(this.stringLength)
   }
 }
 

libraries/overleaf-editor-core/lib/file_data/index.js

@@ -15,6 +15,7 @@ let StringFileData = null
 
 /**
  * @typedef {import("../types").BlobStore} BlobStore
+ * @typedef {import("../operation/edit_operation")} EditOperation
  * @typedef {import("../types").CommentRawData} CommentRawData
  */
 
@@ -62,33 +63,52 @@ class FileData {
     throw new Error('FileData: toRaw not implemented')
   }
 
-  /** @see File#getHash */
+  /**
+   * @see File#getHash
+   * @return {string | null | undefined}
+   */
+
   getHash() {
     return null
   }
 
-  /** @see File#getContent */
+  /**
+   * @see File#getContent
+   * @return {string | null | undefined}
+   */
   getContent() {
     return null
   }
 
-  /** @see File#isEditable */
+  /**
+   * @see File#isEditable
+   * @return {boolean | null | undefined} null if it is not currently known
+   */
   isEditable() {
     return null
   }
 
-  /** @see File#getByteLength */
+  /**
+   * @see File#getByteLength
+   * @return {number | null | undefined}
+   */
   getByteLength() {
     return null
   }
 
-  /** @see File#getStringLength */
+  /**
+   * @see File#getStringLength
+   * @return {number | null | undefined}
+   */
   getStringLength() {
     return null
   }
 
-  /** @see File#edit */
-  edit(textOperation) {
+  /**
+   * @see File#edit
+   * @param {EditOperation} editOperation
+   */
+  edit(editOperation) {
     throw new Error('edit not implemented for ' + JSON.stringify(this))
   }
 

libraries/overleaf-editor-core/lib/file_data/lazy_string_file_data.js

@@ -1,3 +1,4 @@
+// @ts-check
 'use strict'
 
 const _ = require('lodash')
@@ -6,40 +7,41 @@ const assert = require('check-types').assert
 const Blob = require('../blob')
 const FileData = require('./')
 const EagerStringFileData = require('./string_file_data')
-const TextOperation = require('../operation/text_operation')
+const EditOperation = require('../operation/edit_operation')
+const EditOperationBuilder = require('../operation/edit_operation_builder')
 
 class LazyStringFileData extends FileData {
   /**
    * @param {string} hash
    * @param {number} stringLength
-   * @param {Array.<TextOperation>} [textOperations]
+   * @param {Array.<EditOperation>} [operations]
    * @see FileData
    */
-  constructor(hash, stringLength, textOperations) {
+  constructor(hash, stringLength, operations) {
     super()
     assert.match(hash, Blob.HEX_HASH_RX)
     assert.greaterOrEqual(stringLength, 0)
-    assert.maybe.array.of.instance(textOperations, TextOperation)
+    assert.maybe.array.of.instance(operations, EditOperation)
 
     this.hash = hash
     this.stringLength = stringLength
-    this.textOperations = textOperations || []
+    this.operations = operations || []
   }
 
   static fromRaw(raw) {
     return new LazyStringFileData(
       raw.hash,
       raw.stringLength,
-      raw.textOperations && _.map(raw.textOperations, TextOperation.fromJSON)
+      raw.operations && _.map(raw.operations, EditOperationBuilder.fromJSON)
     )
   }
 
   /** @inheritdoc */
   toRaw() {
     const raw = { hash: this.hash, stringLength: this.stringLength }
-    if (this.textOperations.length) {
-      raw.textOperations = _.map(this.textOperations, function (textOperation) {
-        return textOperation.toJSON()
+    if (this.operations.length) {
+      raw.operations = _.map(this.operations, function (operation) {
+        return operation.toJSON()
       })
     }
     return raw
@@ -47,7 +49,7 @@ class LazyStringFileData extends FileData {
 
   /** @inheritdoc */
   getHash() {
-    if (this.textOperations.length) return null
+    if (this.operations.length) return null
     return this.hash
   }
 
@@ -76,16 +78,21 @@ class LazyStringFileData extends FileData {
    * Get the cached text operations that are to be applied to this file to get
    * from the content with its last known hash to its latest content.
    *
-   * @return {Array.<TextOperation>}
+   * @return {Array.<EditOperation>}
    */
-  getTextOperations() {
-    return this.textOperations
+  getOperations() {
+    return this.operations
   }
 
-  /** @inheritdoc */
+  /**
+   * @inheritdoc
+   * @returns {Promise<EagerStringFileData>}
+   */
   async toEager(blobStore) {
     const content = await blobStore.getString(this.hash)
-    return new EagerStringFileData(computeContent(this.textOperations, content))
+    const file = new EagerStringFileData(content)
+    applyOperations(this.operations, file)
+    return file
   }
 
   /** @inheritdoc */
@@ -99,33 +106,30 @@ class LazyStringFileData extends FileData {
   }
 
   /** @inheritdoc */
-  edit(textOperation) {
-    this.stringLength = textOperation.applyToLength(this.stringLength)
-    this.textOperations.push(textOperation)
+  edit(operation) {
+    this.stringLength = operation.applyToLength(this.stringLength)
+    this.operations.push(operation)
   }
 
   /** @inheritdoc */
   async store(blobStore) {
-    if (this.textOperations.length === 0) {
+    if (this.operations.length === 0) {
       return { hash: this.hash }
     }
-
-    const content = await blobStore.getString(this.hash)
-    const blob = await blobStore.putString(
-      computeContent(this.textOperations, content)
-    )
-    this.hash = blob.getHash()
-    this.stringLength = blob.getStringLength()
-    this.textOperations.length = 0
-    return { hash: this.hash }
+    const eager = await this.toEager(blobStore)
+    this.operations.length = 0
+    return eager.store(blobStore)
   }
 }
 
-function computeContent(textOperations, initialFile) {
-  function applyTextOperation(content, textOperation) {
-    return textOperation.apply(content)
-  }
-  return _.reduce(textOperations, applyTextOperation, initialFile)
+/**
+ *
+ * @param {EditOperation[]} operations
+ * @param {EagerStringFileData} file
+ * @returns {void}
+ */
+function applyOperations(operations, file) {
+  _.each(operations, operation => operation.apply(file))
 }
 
 module.exports = LazyStringFileData

libraries/overleaf-editor-core/lib/file_data/string_file_data.js

@@ -1,3 +1,4 @@
+// @ts-check
 'use strict'
 
 const assert = require('check-types').assert
@@ -7,6 +8,8 @@ const CommentList = require('./comment_list')
 
 /**
  * @typedef {import("../types").StringFileRawData} StringFileRawData
+ * @typedef {import("../operation/edit_operation")} EditOperation
+ * @typedef {import("../types").BlobStore} BlobStore
  * @typedef {import("../types").CommentRawData} CommentRawData
  */
 
@@ -65,9 +68,11 @@ class StringFileData extends FileData {
     return this.content.length
   }
 
-  /** @inheritdoc */
-  edit(textOperation) {
-    this.content = textOperation.apply(this.content)
+  /**
+   * @inheritdoc
+   * @param {EditOperation} operation */
+  edit(operation) {
+    operation.apply(this)
   }
 
   /** @inheritdoc */
@@ -75,7 +80,10 @@ class StringFileData extends FileData {
     return this.comments.getComments()
   }
 
-  /** @inheritdoc */
+  /**
+   * @inheritdoc
+   * @returns {Promise<StringFileData>}
+   */
   async toEager() {
     return this
   }
@@ -85,7 +93,10 @@ class StringFileData extends FileData {
     return FileData.createHollow(this.getByteLength(), this.getStringLength())
   }
 
-  /** @inheritdoc */
+  /**
+   * @inheritdoc
+   * @param {BlobStore} blobStore
+   */
   async store(blobStore) {
     const blob = await blobStore.putString(this.content)
     return { hash: blob.getHash() }

libraries/overleaf-editor-core/lib/operation/edit_file_operation.js

@@ -1,20 +1,22 @@
+// @ts-check
 'use strict'
+/** @typedef {import('./edit_operation')} EditOperation */
 
 const Operation = require('./')
-const TextOperation = require('./text_operation')
+const EditOperationBuilder = require('./edit_operation_builder')
 
 /**
- * Edit a file in place. It is a wrapper around a single TextOperation.
+ * Edit a file in place. It is a wrapper around a single EditOperation.
  */
 class EditFileOperation extends Operation {
   /**
    * @param {string} pathname
-   * @param {TextOperation} textOperation
+   * @param {EditOperation} operation
    */
-  constructor(pathname, textOperation) {
+  constructor(pathname, operation) {
     super()
     this.pathname = pathname
-    this.textOperation = textOperation
+    this.operation = operation
   }
 
   /**
@@ -23,7 +25,7 @@ class EditFileOperation extends Operation {
   toRaw() {
     return {
       pathname: this.pathname,
-      textOperation: this.textOperation.toJSON(),
+      ...this.operation.toJSON(),
     }
   }
 
@@ -36,7 +38,7 @@ class EditFileOperation extends Operation {
   static fromRaw(raw) {
     return new EditFileOperation(
       raw.pathname,
-      TextOperation.fromJSON(raw.textOperation)
+      EditOperationBuilder.fromJSON(raw)
     )
   }
 
@@ -44,15 +46,15 @@ class EditFileOperation extends Operation {
     return this.pathname
   }
 
-  getTextOperation() {
-    return this.textOperation
+  getOperation() {
+    return this.operation
   }
 
   /**
    * @inheritdoc
    */
   applyTo(snapshot) {
-    snapshot.editFile(this.pathname, this.textOperation)
+    snapshot.editFile(this.pathname, this.operation)
   }
 
   /**
@@ -61,7 +63,7 @@ class EditFileOperation extends Operation {
   canBeComposedWithForUndo(other) {
     return (
       this.canBeComposedWith(other) &&
-      this.textOperation.canBeComposedWithForUndo(other.textOperation)
+      this.operation.canBeComposedWithForUndo(other.operation)
     )
   }
 
@@ -74,7 +76,7 @@ class EditFileOperation extends Operation {
     // Ensure that both operations are editing the same file
     if (this.getPathname() !== other.getPathname()) return false
 
-    return this.textOperation.canBeComposedWith(other.textOperation)
+    return this.operation.canBeComposedWith(other.operation)
   }
 
   /**
@@ -83,7 +85,7 @@ class EditFileOperation extends Operation {
   compose(other) {
     return new EditFileOperation(
       this.pathname,
-      this.textOperation.compose(other.textOperation)
+      this.operation.compose(other.operation)
     )
   }
 }

libraries/overleaf-editor-core/lib/operation/edit_operation.js

@@ -0,0 +1,90 @@
+// @ts-check
+/**
+ * @typedef {import('../file_data')} FileData
+ */
+
+class EditOperation {
+  constructor() {
+    if (this.constructor === EditOperation) {
+      throw new Error('Cannot instantiate abstract class')
+    }
+  }
+
+  /**
+   * Converts operation into a JSON value.
+   * @returns {object}
+   */
+  toJSON() {
+    throw new Error('Abstract method not implemented')
+  }
+
+  /**
+   * @abstract
+   * @param {FileData} fileData
+   */
+  apply(fileData) {
+    throw new Error('Abstract method not implemented')
+  }
+
+  /**
+   * Determine the effect of this operation on the length of the text.
+   *
+   * NB: This is an Overleaf addition to the original OT system.
+   *
+   * @param {number} length of the original string; non-negative
+   * @return {number} length of the new string; non-negative
+   */
+  applyToLength(length) {
+    return length
+  }
+
+  /**
+   * Computes the inverse of an operation. The inverse of an operation is the
+   * operation that reverts the effects of the operation, e.g. when you have an
+   * operation 'insert("hello "); skip(6);' then the inverse is 'remove("hello ");
+   * skip(6);'. The inverse should be used for implementing undo.
+   * @param {FileData} previousState
+   * @returns {EditOperation}
+   */
+  invert(previousState) {
+    throw new Error('Abstract method not implemented')
+  }
+
+  /**
+   *
+   * @param {EditOperation} other
+   * @returns {boolean}
+   */
+  canBeComposedWith(other) {
+    return false
+  }
+
+  /**
+   * When you use ctrl-z to undo your latest changes, you expect the program not
+   * to undo every single keystroke but to undo your last sentence you wrote at
+   * a stretch or the deletion you did by holding the backspace key down. This
+   * This can be implemented by composing operations on the undo stack. This
+   * method can help decide whether two operations should be composed. It
+   * returns true if the operations are consecutive insert operations or both
+   * operations delete text at the same position. You may want to include other
+   * factors like the time since the last change in your decision.
+   * @param {EditOperation} other
+   */
+  canBeComposedWithForUndo(other) {
+    return false
+  }
+
+  /**
+   * Compose merges two consecutive operations into one operation, that
+   * preserves the changes of both. Or, in other words, for each input string S
+   * and a pair of consecutive operations A and B,
+   * apply(apply(S, A), B) = apply(S, compose(A, B)) must hold.
+   * @param {EditOperation} other
+   * @returns {EditOperation}
+   */
+  compose(other) {
+    throw new Error('Abstract method not implemented')
+  }
+}
+
+module.exports = EditOperation

libraries/overleaf-editor-core/lib/operation/edit_operation_builder.js

@@ -0,0 +1,19 @@
+// @ts-check
+/** @typedef {import('./edit_operation')} EditOperation */
+const TextOperation = require('./text_operation')
+
+class EditOperationBuilder {
+  /**
+   *
+   * @param {object} raw
+   * @returns {EditOperation}
+   */
+  static fromJSON(raw) {
+    if (raw.textOperation) {
+      return TextOperation.fromJSON(raw)
+    }
+    throw new Error('Unsupported operation in EditOperationBuilder.fromJSON')
+  }
+}
+
+module.exports = EditOperationBuilder

libraries/overleaf-editor-core/lib/operation/edit_operation_transformer.js

@@ -0,0 +1,21 @@
+// @ts-check
+const TextOperation = require('./text_operation')
+/** @typedef {import('./edit_operation')} EditOperation */
+
+class EditOperationTransformer {
+  /**
+   * Transform two edit operations against each other.
+   * @param {EditOperation} a
+   * @param {EditOperation} b
+   */
+  static transform(a, b) {
+    if (a instanceof TextOperation && b instanceof TextOperation) {
+      return TextOperation.transform(a, b)
+    }
+    throw new Error(
+      `Transform not implemented for ${a.constructor.name}￮${b.constructor.name}`
+    )
+  }
+}
+
+module.exports = EditOperationTransformer

libraries/overleaf-editor-core/lib/operation/index.js

@@ -2,8 +2,7 @@
 
 const _ = require('lodash')
 const assert = require('check-types').assert
-
-const TextOperation = require('./text_operation')
+const EditOperationTransformer = require('./edit_operation_transformer')
 
 // Dependencies are loaded at the bottom of the file to mitigate circular
 // dependency
@@ -224,8 +223,8 @@ class Operation {
     return new AddFileOperation(pathname, file)
   }
 
-  static editFile(pathname, textOperation) {
-    return new EditFileOperation(pathname, textOperation)
+  static editFile(pathname, editOperation) {
+    return new EditFileOperation(pathname, editOperation)
   }
 
   static moveFile(pathname, newPathname) {
@@ -390,7 +389,7 @@ function transformMoveFileEditFile(move, edit) {
     }
     return [
       move,
-      Operation.editFile(move.getNewPathname(), edit.getTextOperation()),
+      Operation.editFile(move.getNewPathname(), edit.getOperation()),
     ]
   }
 
@@ -422,13 +421,13 @@ function transformMoveFileSetFileMetadata(move, set) {
 
 function transformEditFileEditFile(edit1, edit2) {
   if (edit1.getPathname() === edit2.getPathname()) {
-    const primeTextOps = TextOperation.transform(
-      edit1.getTextOperation(),
-      edit2.getTextOperation()
+    const primeOps = EditOperationTransformer.transform(
+      edit1.getOperation(),
+      edit2.getOperation()
     )
     return [
-      Operation.editFile(edit1.getPathname(), primeTextOps[0]),
-      Operation.editFile(edit2.getPathname(), primeTextOps[1]),
+      Operation.editFile(edit1.getPathname(), primeOps[0]),
+      Operation.editFile(edit2.getPathname(), primeOps[1]),
     ]
   }
 

libraries/overleaf-editor-core/lib/operation/text_operation.js

@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * The text operation from OT.js with some minor cosmetic changes.
  *
@@ -8,10 +9,10 @@
  */
 
 'use strict'
-
 const containsNonBmpChars = require('../util').containsNonBmpChars
-
 const OError = require('@overleaf/o-error')
+const EditOperation = require('./edit_operation')
+/** @typedef {import('../file_data/string_file_data')} StringFileData */
 
 class UnprocessableError extends OError {}
 
@@ -44,8 +45,9 @@ class TooLongError extends UnprocessableError {
 
 /**
  * Create an empty text operation.
+ * @extends EditOperation
  */
-class TextOperation {
+class TextOperation extends EditOperation {
   /**
    * Length of the longest file that we'll attempt to edit, in characters.
    *
@@ -61,6 +63,7 @@ class TextOperation {
   static isRemove = isRemove
 
   constructor() {
+    super()
     // When an operation is applied to an input string, you can think of this as
     // if an imaginary cursor runs over the entire string and skips over some
     // parts, removes some parts and inserts characters at some positions. These
@@ -206,16 +209,16 @@ class TextOperation {
   }
 
   /**
-   * Converts operation into a JSON value.
+   * @inheritdoc
    */
   toJSON() {
-    return this.ops
+    return { textOperation: this.ops }
   }
 
   /**
    * Converts a plain JS object into an operation and validates it.
    */
-  static fromJSON = function (ops) {
+  static fromJSON = function ({ textOperation: ops }) {
     const o = new TextOperation()
     for (let i = 0, l = ops.length; i < l; i++) {
       const op = ops[i]
@@ -240,8 +243,12 @@ class TextOperation {
   /**
    * Apply an operation to a string, returning a new string. Throws an error if
    * there's a mismatch between the input string and the operation.
+   * @override
+   * @inheritdoc
+   * @param {StringFileData} file
    */
-  apply(str) {
+  apply(file) {
+    const str = file.getContent()
     const operation = this
     if (containsNonBmpChars(str)) {
       throw new TextOperation.ApplyError(
@@ -298,16 +305,12 @@ class TextOperation {
     if (result.length > TextOperation.MAX_STRING_LENGTH) {
       throw new TextOperation.TooLongError(operation, result.length)
     }
-    return result
+
+    file.content = result
   }
 
   /**
-   * Determine the effect of this operation on the length of the text.
-   *
-   * NB: This is an Overleaf addition to the original TextOperation.
-   *
-   * @param {number} length of the original string; non-negative
-   * @return {number} length of the new string; non-negative
+   * @inheritdoc
    */
   applyToLength(length) {
     const operation = this
@@ -356,12 +359,11 @@ class TextOperation {
   }
 
   /**
-   * Computes the inverse of an operation. The inverse of an operation is the
-   * operation that reverts the effects of the operation, e.g. when you have an
-   * operation 'insert("hello "); skip(6);' then the inverse is 'remove("hello ");
-   * skip(6);'. The inverse should be used for implementing undo.
+   * @inheritdoc
+   * @param {StringFileData} previousState
    */
-  invert(str) {
+  invert(previousState) {
+    const str = previousState.getContent()
     let strIndex = 0
     const inverse = new TextOperation()
     const ops = this.ops
@@ -382,16 +384,14 @@ class TextOperation {
   }
 
   /**
-   * When you use ctrl-z to undo your latest changes, you expect the program not
-   * to undo every single keystroke but to undo your last sentence you wrote at
-   * a stretch or the deletion you did by holding the backspace key down. This
-   * This can be implemented by composing operations on the undo stack. This
-   * method can help decide whether two operations should be composed. It
-   * returns true if the operations are consecutive insert operations or both
-   * operations delete text at the same position. You may want to include other
-   * factors like the time since the last change in your decision.
+   * @inheritdoc
+   * @param {EditOperation} other
    */
   canBeComposedWithForUndo(other) {
+    if (!(other instanceof TextOperation)) {
+      return false
+    }
+
     if (this.isNoop() || other.isNoop()) {
       return true
     }
@@ -419,16 +419,25 @@ class TextOperation {
 
   /**
    * @inheritdoc
+   * @param {EditOperation} other
    */
   canBeComposedWith(other) {
+    if (!(other instanceof TextOperation)) {
+      return false
+    }
     return this.targetLength === other.baseLength
   }
 
-  // Compose merges two consecutive operations into one operation, that
-  // preserves the changes of both. Or, in other words, for each input string S
-  // and a pair of consecutive operations A and B,
-  // apply(apply(S, A), B) = apply(S, compose(A, B)) must hold.
+  /**
+   * @inheritdoc
+   * @param {EditOperation} operation2
+   */
   compose(operation2) {
+    if (!(operation2 instanceof TextOperation)) {
+      throw new Error(
+        `Trying to compose TextOperation with ${operation2?.constructor?.name}.`
+      )
+    }
     const operation1 = this
     if (operation1.targetLength !== operation2.baseLength) {
       throw new Error(
@@ -543,6 +552,8 @@ class TextOperation {
    * produces two operations A' and B' (in an array) such that
    * `apply(apply(S, A), B') = apply(apply(S, B), A')`. This function is the
    * heart of OT.
+   * @param {TextOperation} operation1
+   * @param {TextOperation} operation2
    */
   static transform(operation1, operation2) {
     if (operation1.baseLength !== operation2.baseLength) {

libraries/overleaf-editor-core/test/edit_file_operation.test.js

@@ -1,17 +1,18 @@
+// @ts-check
 'use strict'
 
 const { expect } = require('chai')
 
 const ot = require('..')
+const EditOperationBuilder = require('../lib/operation/edit_operation_builder')
 const File = ot.File
 const Operation = ot.Operation
-const TextOperation = ot.TextOperation
 
 describe('EditFileOperation', function () {
   function edit(pathname, textOperationJsonObject) {
     return Operation.editFile(
       pathname,
-      TextOperation.fromJSON(textOperationJsonObject)
+      EditOperationBuilder.fromJSON({ textOperation: textOperationJsonObject })
     )
   }
 

libraries/overleaf-editor-core/test/edit_operation.test.js

@@ -0,0 +1,55 @@
+const { expect } = require('chai')
+const EditOperationBuilder = require('../lib/operation/edit_operation_builder')
+const TextOperation = require('../lib/operation/text_operation')
+const EditOperationTransformer = require('../lib/operation/edit_operation_transformer')
+const EditOperation = require('../lib/operation/edit_operation')
+const randomTextOperation = require('./support/random_text_operation')
+const random = require('./support/random')
+
+describe('EditOperation', function () {
+  it('Cannot be instantiated', function () {
+    expect(() => new EditOperation()).to.throw(
+      'Cannot instantiate abstract class'
+    )
+  })
+})
+
+describe('EditOperationTransformer', function () {
+  it('Transforms two TextOperations', function () {
+    const a = new TextOperation().insert('foo')
+    const b = new TextOperation().insert('bar')
+    const [aPrime, bPrime] = EditOperationTransformer.transform(a, b)
+    expect(aPrime).to.be.an.instanceof(TextOperation)
+    expect(bPrime).to.be.an.instanceof(TextOperation)
+  })
+})
+
+describe('EditOperationBuilder', function () {
+  it('Constructs TextOperation from JSON', function () {
+    const raw = {
+      textOperation: [1, 'foo', 3],
+    }
+    const op = EditOperationBuilder.fromJSON(raw)
+    expect(op).to.be.an.instanceof(TextOperation)
+    expect(op.ops).to.deep.equal([1, 'foo', 3])
+  })
+
+  it('Throws error for unsupported operation', function () {
+    const raw = {
+      unsupportedOperation: {
+        op: 'foo',
+      },
+    }
+    expect(() => EditOperationBuilder.fromJSON(raw)).to.throw(
+      'Unsupported operation in EditOperationBuilder.fromJSON'
+    )
+  })
+
+  it('Constructs TextOperation from JSON (randomised)', function () {
+    const str = random.string(50)
+    const randomOperation = randomTextOperation(str)
+    const op = EditOperationBuilder.fromJSON(randomOperation.toJSON())
+    expect(op).to.be.an.instanceof(TextOperation)
+    expect(op.equals(randomOperation)).to.be.true
+  })
+})

libraries/overleaf-editor-core/test/lazy_string_file_data.test.js

@@ -21,32 +21,32 @@ describe('LazyStringFileData', function () {
     roundTripFileData = LazyStringFileData.fromRaw(fileData.toRaw())
     expect(roundTripFileData.getHash()).to.equal(testHash)
     expect(roundTripFileData.getStringLength()).to.equal(0)
-    expect(roundTripFileData.getTextOperations()).to.have.length(0)
+    expect(roundTripFileData.getOperations()).to.have.length(0)
 
     fileData.edit(new TextOperation().insert('a'))
     expect(fileData.toRaw()).to.eql({
       hash: testHash,
       stringLength: 1,
-      textOperations: [['a']],
+      operations: [{ textOperation: ['a'] }],
     })
     roundTripFileData = LazyStringFileData.fromRaw(fileData.toRaw())
     expect(roundTripFileData.getHash()).not.to.exist // file has changed
     expect(roundTripFileData.getStringLength()).to.equal(1)
-    expect(roundTripFileData.getTextOperations()).to.have.length(1)
-    expect(roundTripFileData.getTextOperations()[0].ops).to.have.length(1)
+    expect(roundTripFileData.getOperations()).to.have.length(1)
+    expect(roundTripFileData.getOperations()[0].ops).to.have.length(1)
 
     fileData.edit(new TextOperation().retain(1).insert('b'))
     expect(fileData.toRaw()).to.eql({
       hash: testHash,
       stringLength: 2,
-      textOperations: [['a'], [1, 'b']],
+      operations: [{ textOperation: ['a'] }, { textOperation: [1, 'b'] }],
     })
     roundTripFileData = LazyStringFileData.fromRaw(fileData.toRaw())
     expect(roundTripFileData.getHash()).not.to.exist // file has changed
     expect(roundTripFileData.getStringLength()).to.equal(2)
-    expect(roundTripFileData.getTextOperations()).to.have.length(2)
-    expect(roundTripFileData.getTextOperations()[0].ops).to.have.length(1)
-    expect(roundTripFileData.getTextOperations()[1].ops).to.have.length(2)
+    expect(roundTripFileData.getOperations()).to.have.length(2)
+    expect(roundTripFileData.getOperations()[0].ops).to.have.length(1)
+    expect(roundTripFileData.getOperations()[1].ops).to.have.length(2)
   })
 
   it('validates operations when edited', function () {
@@ -55,13 +55,13 @@ describe('LazyStringFileData', function () {
     expect(fileData.getHash()).equal(testHash)
     expect(fileData.getByteLength()).to.equal(0) // approximately
     expect(fileData.getStringLength()).to.equal(0)
-    expect(fileData.getTextOperations()).to.have.length(0)
+    expect(fileData.getOperations()).to.have.length(0)
 
     fileData.edit(new TextOperation().insert('a'))
     expect(fileData.getHash()).not.to.exist
     expect(fileData.getByteLength()).to.equal(1) // approximately
     expect(fileData.getStringLength()).to.equal(1)
-    expect(fileData.getTextOperations()).to.have.length(1)
+    expect(fileData.getOperations()).to.have.length(1)
 
     expect(() => {
       fileData.edit(new TextOperation().retain(10))
@@ -69,7 +69,7 @@ describe('LazyStringFileData', function () {
     expect(fileData.getHash()).not.to.exist
     expect(fileData.getByteLength()).to.equal(1) // approximately
     expect(fileData.getStringLength()).to.equal(1)
-    expect(fileData.getTextOperations()).to.have.length(1)
+    expect(fileData.getOperations()).to.have.length(1)
   })
 
   it('validates string length when edited', function () {
@@ -78,14 +78,14 @@ describe('LazyStringFileData', function () {
     expect(fileData.getHash()).equal(testHash)
     expect(fileData.getByteLength()).to.equal(0) // approximately
     expect(fileData.getStringLength()).to.equal(0)
-    expect(fileData.getTextOperations()).to.have.length(0)
+    expect(fileData.getOperations()).to.have.length(0)
 
     const longString = _.repeat('a', TextOperation.MAX_STRING_LENGTH)
     fileData.edit(new TextOperation().insert(longString))
     expect(fileData.getHash()).not.to.exist
     expect(fileData.getByteLength()).to.equal(longString.length) // approximate
     expect(fileData.getStringLength()).to.equal(longString.length)
-    expect(fileData.getTextOperations()).to.have.length(1)
+    expect(fileData.getOperations()).to.have.length(1)
 
     expect(() => {
       fileData.edit(new TextOperation().retain(longString.length).insert('x'))
@@ -93,6 +93,6 @@ describe('LazyStringFileData', function () {
     expect(fileData.getHash()).not.to.exist
     expect(fileData.getByteLength()).to.equal(longString.length) // approximate
     expect(fileData.getStringLength()).to.equal(longString.length)
-    expect(fileData.getTextOperations()).to.have.length(1)
+    expect(fileData.getOperations()).to.have.length(1)
   })
 })

libraries/overleaf-editor-core/test/operation.test.js

@@ -114,10 +114,10 @@ describe('Operation', function () {
   }
 
   // shorthand for creating an edit operation
-  function edit(pathname, textOperationJsonObject) {
+  function edit(pathname, textOperationOps) {
     return Operation.editFile(
       pathname,
-      TextOperation.fromJSON(textOperationJsonObject)
+      TextOperation.fromJSON({ textOperation: textOperationOps })
     )
   }
 
@@ -633,14 +633,12 @@ describe('Operation', function () {
       .expectPrime(1, EditFileOperation)
       .expectPrime(0, EditFileOperation)
       .tap(function () {
-        expect(this.primeOperations[1].getTextOperation().toJSON()).to.eql([
-          1,
-          'y',
-        ])
-        expect(this.primeOperations[0].getTextOperation().toJSON()).to.eql([
-          'x',
-          1,
-        ])
+        expect(this.primeOperations[1].getOperation().toJSON()).to.eql({
+          textOperation: [1, 'y'],
+        })
+        expect(this.primeOperations[0].getOperation().toJSON()).to.eql({
+          textOperation: ['x', 1],
+        })
       })
       .swap()
       .expectFiles({ foo: 'yx' })

libraries/overleaf-editor-core/test/support/random_text_operation.js

@@ -0,0 +1,31 @@
+const TextOperation = require('../../lib/operation/text_operation')
+const random = require('./random')
+
+/**
+ *
+ * @param {string} str
+ * @returns {TextOperation}
+ */
+function randomTextOperation(str) {
+  const operation = new TextOperation()
+  let left
+  while (true) {
+    left = str.length - operation.baseLength
+    if (left === 0) break
+    const r = Math.random()
+    const l = 1 + random.int(Math.min(left - 1, 20))
+    if (r < 0.2) {
+      operation.insert(random.string(l))
+    } else if (r < 0.4) {
+      operation.remove(l)
+    } else {
+      operation.retain(l)
+    }
+  }
+  if (Math.random() < 0.3) {
+    operation.insert(1 + random.string(10))
+  }
+  return operation
+}
+
+module.exports = randomTextOperation

libraries/overleaf-editor-core/test/text_operation.test.js

@@ -7,31 +7,11 @@
 
 const { expect } = require('chai')
 const random = require('./support/random')
+const randomOperation = require('./support/random_text_operation')
 
 const ot = require('..')
 const TextOperation = ot.TextOperation
-
-function randomOperation(str) {
-  const operation = new TextOperation()
-  let left
-  while (true) {
-    left = str.length - operation.baseLength
-    if (left === 0) break
-    const r = Math.random()
-    const l = 1 + random.int(Math.min(left - 1, 20))
-    if (r < 0.2) {
-      operation.insert(random.string(l))
-    } else if (r < 0.4) {
-      operation.remove(l)
-    } else {
-      operation.retain(l)
-    }
-  }
-  if (Math.random() < 0.3) {
-    operation.insert(1 + random.string(10))
-  }
-  return operation
-}
+const StringFileData = require('../lib/file_data/string_file_data')
 
 describe('TextOperation', function () {
   const numTrials = 500
@@ -134,7 +114,7 @@ describe('TextOperation', function () {
 
   it('converts from JSON', function () {
     const ops = [2, -1, -1, 'cde']
-    const o = TextOperation.fromJSON(ops)
+    const o = TextOperation.fromJSON({ textOperation: ops })
     expect(o.ops.length).to.equal(3)
     expect(o.baseLength).to.equal(4)
     expect(o.targetLength).to.equal(5)
@@ -143,7 +123,7 @@ describe('TextOperation', function () {
       const ops2 = ops.slice(0)
       fn(ops2)
       expect(() => {
-        TextOperation.fromJSON(ops2)
+        TextOperation.fromJSON({ textOperations: ops2 })
       }).to.throw
     }
 
@@ -161,7 +141,10 @@ describe('TextOperation', function () {
       const str = random.string(50)
       const o = randomOperation(str)
       expect(str.length).to.equal(o.baseLength)
-      expect(o.apply(str).length).to.equal(o.targetLength)
+      const file = new StringFileData(str)
+      o.apply(file)
+      const result = file.getContent()
+      expect(result.length).to.equal(o.targetLength)
     })
   )
 
@@ -170,10 +153,14 @@ describe('TextOperation', function () {
     random.test(numTrials, () => {
       const str = random.string(50)
       const o = randomOperation(str)
-      const p = o.invert(str)
+      const p = o.invert(new StringFileData(str))
       expect(o.baseLength).to.equal(p.targetLength)
       expect(o.targetLength).to.equal(p.baseLength)
-      expect(p.apply(o.apply(str))).to.equal(str)
+      const file = new StringFileData(str)
+      o.apply(file)
+      p.apply(file)
+      const result = file.getContent()
+      expect(result).to.equal(str)
     })
   )
 
@@ -193,14 +180,18 @@ describe('TextOperation', function () {
       // invariant: apply(str, compose(a, b)) === apply(apply(str, a), b)
       const str = random.string(20)
       const a = randomOperation(str)
-      const afterA = a.apply(str)
+      const file = new StringFileData(str)
+      a.apply(file)
+      const afterA = file.getContent()
       expect(afterA.length).to.equal(a.targetLength)
       const b = randomOperation(afterA)
-      const afterB = b.apply(afterA)
+      b.apply(file)
+      const afterB = file.getContent()
       expect(afterB.length).to.equal(b.targetLength)
       const ab = a.compose(b)
       expect(ab.targetLength).to.equal(b.targetLength)
-      const afterAB = ab.apply(str)
+      ab.apply(new StringFileData(str))
+      const afterAB = file.getContent()
       expect(afterAB).to.equal(afterB)
     })
   )
@@ -218,20 +209,22 @@ describe('TextOperation', function () {
       const bPrime = primes[1]
       const abPrime = a.compose(bPrime)
       const baPrime = b.compose(aPrime)
-      const afterAbPrime = abPrime.apply(str)
-      const afterBaPrime = baPrime.apply(str)
+      const abFile = new StringFileData(str)
+      const baFile = new StringFileData(str)
+      abPrime.apply(abFile)
+      baPrime.apply(baFile)
       expect(abPrime.equals(baPrime)).to.be.true
-      expect(afterAbPrime).to.equal(afterBaPrime)
+      expect(abFile.getContent()).to.equal(baFile.getContent())
     })
   )
 
   it('throws when invalid operations are applied', function () {
     const operation = new TextOperation().retain(1)
     expect(() => {
-      operation.apply('')
+      operation.apply(new StringFileData(''))
     }).to.throw(TextOperation.ApplyError)
     expect(() => {
-      operation.apply(' ')
+      operation.apply(new StringFileData(' '))
     }).not.to.throw
   })
 
@@ -250,7 +243,7 @@ describe('TextOperation', function () {
     const operation = new TextOperation()
     const str = '𝌆\n'
     expect(() => {
-      operation.apply(str)
+      operation.apply(new StringFileData(str))
     }).to.throw(
       TextOperation.UnprocessableError,
       /string contains non BMP characters/
@@ -260,7 +253,7 @@ describe('TextOperation', function () {
   it('throws at from JSON when it contains non BMP chars', function () {
     const operation = ['𝌆\n']
     expect(() => {
-      TextOperation.fromJSON(operation)
+      TextOperation.fromJSON({ textOperation: operation })
     }).to.throw(
       TextOperation.UnprocessableError,
       /inserted text contains non BMP characters/

services/history-v1/test/acceptance/js/api/end_to_end.test.js

@@ -212,7 +212,12 @@ describe('overleaf ot', function () {
         // edit the main file
         .then(projectId => {
           const change = new Change(
-            [Operation.editFile('main.tex', TextOperation.fromJSON(['hello']))],
+            [
+              Operation.editFile(
+                'main.tex',
+                TextOperation.fromJSON({ textOperation: ['hello'] })
+              ),
+            ],
             new Date()
           )
           return basicAuthClient.apis.ProjectImport.importChanges1({
@@ -263,7 +268,7 @@ describe('overleaf ot', function () {
             [
               Operation.editFile(
                 'main.tex',
-                TextOperation.fromJSON([1, -4, 'i world'])
+                TextOperation.fromJSON({ textOperation: [1, -4, 'i world'] })
               ),
             ],
             new Date()

services/history-v1/test/acceptance/js/api/project_updates.test.js

@@ -49,8 +49,10 @@ describe('history import', function () {
     const testProjectId = '1'
     const testFilePathname = 'main.tex'
     const testAuthors = [123, null]
-    const testTextOperation0 = TextOperation.fromJSON(['a'])
-    const testTextOperation1 = TextOperation.fromJSON([1, 'b'])
+    const testTextOperation0 = TextOperation.fromJSON({ textOperation: ['a'] })
+    const testTextOperation1 = TextOperation.fromJSON({
+      textOperation: [1, 'b'],
+    })
 
     let testSnapshot
 
@@ -188,7 +190,9 @@ describe('history import', function () {
   it('rejects invalid changes in history', function () {
     const testProjectId = '1'
     const testFilePathname = 'main.tex'
-    const testTextOperation = TextOperation.fromJSON(['a', 10])
+    const testTextOperation = TextOperation.fromJSON({
+      textOperation: ['a', 10],
+    })
 
     let testSnapshot
 
@@ -286,7 +290,7 @@ describe('history import', function () {
     const testProjectId = '1'
     const mainFilePathname = 'main.tex'
     const testFilePathname = 'test.tex'
-    const testTextOperation = TextOperation.fromJSON(['a'])
+    const testTextOperation = TextOperation.fromJSON({ textOperation: ['a'] })
     const inexistentAuthors = [1234, 5678]
     const projectVersion = '12345.0'
     const v2DocVersions = new V2DocVersions({
@@ -447,7 +451,7 @@ describe('history import', function () {
   it('rejects text operations on binary files', function () {
     const testProjectId = '1'
     const testFilePathname = 'main.tex'
-    const testTextOperation = TextOperation.fromJSON(['bb'])
+    const testTextOperation = TextOperation.fromJSON({ textOperation: ['bb'] })
 
     let testSnapshot
 
@@ -517,7 +521,9 @@ describe('history import', function () {
   it('accepts text operation on files with null characters if stringLength is present', function () {
     const testProjectId = '1'
     const mainFilePathname = 'main.tex'
-    const testTextOperation = TextOperation.fromJSON([3, 'a'])
+    const testTextOperation = TextOperation.fromJSON({
+      textOperation: [3, 'a'],
+    })
 
     let testSnapshot
 
@@ -626,7 +632,7 @@ describe('history import', function () {
 
   it('creates and returns changes with v2 author ids', function () {
     const testFilePathname = 'test.tex'
-    const testTextOperation = TextOperation.fromJSON(['a'])
+    const testTextOperation = TextOperation.fromJSON({ textOperation: ['a'] })
     const v2Authors = ['5a296963ad5e82432674c839', null]
 
     let testProjectId

services/history-v1/test/acceptance/js/storage/chunk_store.test.js

@@ -52,7 +52,9 @@ describe('chunkStore', function () {
 
       describe('adding and editing a blank file', function () {
         const testPathname = 'foo.txt'
-        const testTextOperation = TextOperation.fromJSON(['a']) // insert an a
+        const testTextOperation = TextOperation.fromJSON({
+          textOperation: ['a'],
+        }) // insert an a
         let lastChangeTimestamp
 
         beforeEach(async function () {
@@ -259,7 +261,9 @@ describe('chunkStore', function () {
         it('does not create chunks', async function () {
           const oldEndVersion = 0
           const testPathname = 'foo.txt'
-          const testTextOperation = TextOperation.fromJSON(['a']) // insert an a
+          const testTextOperation = TextOperation.fromJSON({
+            textOperation: ['a'],
+          }) // insert an a
 
           let chunk = await chunkStore.loadLatest(projectId)
           expect(chunk.getEndVersion()).to.equal(oldEndVersion)
@@ -287,13 +291,13 @@ describe('chunkStore', function () {
               makeChange(
                 Operation.editFile(
                   'main.tex',
-                  TextOperation.fromJSON([3, 'def'])
+                  TextOperation.fromJSON({ textOperation: [3, 'def'] })
                 )
               ),
               makeChange(
                 Operation.editFile(
                   'main.tex',
-                  TextOperation.fromJSON([6, 'ghi'])
+                  TextOperation.fromJSON({ textOperation: [6, 'ghi'] })
                 )
               ),
             ],

services/project-history/test/unit/js/OperationsCompressor/OperationsCompressorTests.js

@@ -6,7 +6,7 @@ describe('OperationsCompressor', function () {
   function edit(pathname, textOperationJsonObject) {
     return Core.Operation.editFile(
       pathname,
-      Core.TextOperation.fromJSON(textOperationJsonObject)
+      Core.TextOperation.fromJSON({ textOperation: textOperationJsonObject })
     )
   }