Add deleted marker

Author: begor

@types/automerge/index.d.ts

@@ -258,7 +258,7 @@ declare module 'automerge' {
     // (properties that are not changing are not listed). The nested object is
     // empty if the property is being deleted, contains one opId if it is set to
     // a single value, and contains multiple opIds if there is a conflict.
-    props: {[propName: string]: {[opId: string]: MapDiff | ListDiff | ValueDiff }}
+    props: {[propName: string]: {[opId: string]: MapDiff | ListDiff | ValueDiff | '___DELETED___' }}
   }
 
   // Describes changes to a list or Automerge.Text object, in which each element

backend/new.js

@@ -1,4 +1,4 @@
-const { parseOpId, copyObject } = require('../src/common')
+const { parseOpId, copyObject, DELETED_MARKER } = require('../src/common')
 const { COLUMN_TYPE, VALUE_TYPE, ACTIONS, OBJECT_TYPE, DOC_OPS_COLUMNS, CHANGE_COLUMNS, DOCUMENT_COLUMNS,
   encoderByColumnId, decoderByColumnId, makeDecoders, decodeValue,
   encodeChange, decodeChangeColumns, decodeChangeMeta, decodeChanges, decodeDocumentHeader, encodeDocumentHeader } = require('./columnar')
@@ -1021,7 +1021,7 @@ function updatePatchProperty(patches, newBlock, objectId, op, docState, propStat
     } else if (oldSuccNum === 0 && !propState[elemId].action) {
       // If the property used to have a non-overwritten/non-deleted value, but no longer, it's a remove
       propState[elemId].action = 'remove'
-      const removeOpId = `${op[succCtrIdx]}@${docState.actorIds[op[idActorIdx]]}`
+      const removeOpId = `${op[succCtrIdx]}@${docState.actorIds[op[succActorIdx]]}`
       appendEdit(patch.edits, {action: 'remove', index: listIndex, count: 1, opId: removeOpId})
       if (newBlock && newBlock.lastObjectActor === op[objActorIdx] && newBlock.lastObjectCtr === op[objCtrIdx]) {
         newBlock.numVisible -= 1
@@ -1030,7 +1030,21 @@ function updatePatchProperty(patches, newBlock, objectId, op, docState, propStat
 
   } else if (patchValue || !isWholeDoc) {
     // Updating a map or table (with string key)
-    if (firstOp || !patch.props[op[keyStrIdx]]) patch.props[op[keyStrIdx]] = {}
+    if (firstOp || !patch.props[op[keyStrIdx]]) {
+      patch.props[op[keyStrIdx]] = {}
+      // Go over succ (which are successors to this operations) and consider them as deletion operation.
+      // If a succ operation is really a deletion, it'll stay on patch.
+      // If a succ operation isn't a deletion, we'll see it in this function and delete from patch (see below).
+      for (let i = 0; i < op[succNumIdx]; i++) {
+        const succOp = `${op[succCtrIdx][i]}@${docState.actorIds[op[succActorIdx][i]]}`
+        patch.props[op[keyStrIdx]][succOp] = DELETED_MARKER
+      }
+    }
+    // If we look at operation, we know it's not a deletion (we don't store deletions in history).
+    // That means we can delete it from props if earlier we added it when considering it as a delete.
+    if (patch.props[op[keyStrIdx]] !== null && patch.props[op[keyStrIdx]][opId] === DELETED_MARKER) {
+      delete patch.props[op[keyStrIdx]][opId]
+    }
     if (patchValue) patch.props[op[keyStrIdx]][patchKey] = patchValue
   }
 }

frontend/apply_patch.js

@@ -1,4 +1,4 @@
-const { isObject, copyObject, parseOpId } = require('../src/common')
+const { isObject, copyObject, parseOpId, DELETED_MARKER } = require('../src/common')
 const { OBJECT_ID, CONFLICTS, ELEM_IDS } = require('./constants')
 const { instantiateText } = require('./text')
 const { instantiateTable } = require('./table')
@@ -20,6 +20,8 @@ function getValue(patch, object, updated) {
     return new Date(patch.value)
   } else if (patch.datatype === 'counter') {
     return new Counter(patch.value)
+  } else if (patch === DELETED_MARKER) {
+    return DELETED_MARKER;
   } else {
     // Primitive value (int, uint, float64, string, boolean, or null)
     return patch.value
@@ -59,20 +61,25 @@ function applyProperties(props, object, conflicts, updated) {
 
   for (let key of Object.keys(props)) {
     const values = {}, opIds = Object.keys(props[key]).sort(lamportCompare).reverse()
+    const appliedOpIds = []
     for (let opId of opIds) {
       const subpatch = props[key][opId]
+      if (subpatch === DELETED_MARKER) {
+        continue
+      }
+      appliedOpIds.push(opId)
       if (conflicts[key] && conflicts[key][opId]) {
         values[opId] = getValue(subpatch, conflicts[key][opId], updated)
       } else {
         values[opId] = getValue(subpatch, undefined, updated)
       }
     }
 
-    if (opIds.length === 0) {
+    if (appliedOpIds.length === 0) {
       delete object[key]
       delete conflicts[key]
     } else {
-      object[key] = values[opIds[0]]
+      object[key] = values[appliedOpIds[0]]
       conflicts[key] = values
     }
   }

frontend/context.js

@@ -167,7 +167,6 @@ class Context {
       subpatch = values[nextOpId]
       object = this.getPropertyValue(object, pathElem.key, nextOpId)
     }
-
     return subpatch
   }
 

src/common.js

@@ -50,6 +50,8 @@ function createArrayOfNulls(length) {
   return array
 }
 
+const DELETED_MARKER = '___DELETED___'
+
 module.exports = {
-  isObject, copyObject, parseOpId, equalBytes, createArrayOfNulls
+  isObject, copyObject, parseOpId, equalBytes, createArrayOfNulls, DELETED_MARKER
 }

test/backend_test.js

@@ -4,6 +4,7 @@ const Automerge = process.env.TEST_DIST === '1' ? require('../dist/automerge') :
 const Backend = Automerge.Backend
 const { encodeChange, decodeChange } = require('../backend/columnar')
 const uuid = require('../src/uuid')
+const { DELETED_MARKER } = require("../src/common")
 
 function hash(change) {
   return decodeChange(encodeChange(change)).hash
@@ -79,7 +80,7 @@ describe('Automerge.Backend', () => {
       const [s2, patch2] = Backend.applyChanges(s1, [encodeChange(change2)])
       assert.deepStrictEqual(patch2, {
         clock: {[actor]: 2}, deps: [hash(change2)], maxOp: 2, pendingChanges: 0,
-        diffs: {objectId: '_root', type: 'map', props: {bird: {}}}
+        diffs: {objectId: '_root', type: 'map', props: {bird: {[`2@${actor}`]: DELETED_MARKER}}}
       })
     })
 
@@ -132,7 +133,7 @@ describe('Automerge.Backend', () => {
       const [s1, patch1] = Backend.applyChanges(s0, [change1, change2].map(encodeChange))
       assert.deepStrictEqual(patch1, {
         clock: {[actor]: 2}, deps: [hash(change2)], maxOp: 3, pendingChanges: 0,
-        diffs: {objectId: '_root', type: 'map', props: {birds: {}}}
+        diffs: {objectId: '_root', type: 'map', props: {birds: {[`3@${actor}`]: DELETED_MARKER}}}
       })
     })
 
@@ -209,7 +210,7 @@ describe('Automerge.Backend', () => {
       const [s2, patch2] = Backend.applyChanges(s1, [encodeChange(change3)])
       assert.deepStrictEqual(patch1, {
         clock: {[actor1]: 1, [actor2]: 1}, deps: [hash(change2)], maxOp: 3, pendingChanges: 0,
-        diffs: {objectId: '_root', type: 'map', props: {birds: {}}}
+        diffs: {objectId: '_root', type: 'map', props: {birds: {[`3@${actor2}`]: DELETED_MARKER}}}
       })
       assert.deepStrictEqual(patch2, {
         clock: {[actor1]: 2, [actor2]: 1}, deps: [hash(change2), hash(change3)].sort(), maxOp: 3, pendingChanges: 0,
@@ -518,7 +519,7 @@ describe('Automerge.Backend', () => {
                 done: {[`4@${actor1}`]: {type: 'value', value: false}}
               }
             }},
-            {action: 'remove', index: 0, count: 1, opId: `5@${actor1}`}
+            {action: 'remove', index: 0, count: 1, opId: `5@${actor2}`}
           ]
         }}}}
       })

test/new_backend_test.js

@@ -3,6 +3,7 @@ const { checkEncoded } = require('./helpers')
 const { DOC_OPS_COLUMNS, encodeChange, decodeChange } = require('../backend/columnar')
 const { MAX_BLOCK_SIZE, BackendDoc, bloomFilterContains } = require('../backend/new')
 const uuid = require('../src/uuid')
+const { DELETED_MARKER } = require("../src/common")
 
 function checkColumns(block, expectedCols) {
   for (let actual of block.columns) {
@@ -1271,7 +1272,7 @@ describe('BackendDoc applying changes', () => {
     })
     assert.deepStrictEqual(backend.applyChanges([encodeChange(change3)]), {
       maxOp: 3, clock: {[actor]: 3}, deps: [hash(change3)], pendingChanges: 0,
-      diffs: {objectId: '_root', type: 'map', props: {counter: {}}}
+      diffs: {objectId: '_root', type: 'map', props: {counter: {[`3@${actor}`]: DELETED_MARKER}}}
     })
     assert.strictEqual(backend.blocks[0].lastKey, 'counter')
     assert.strictEqual(backend.blocks[0].numOps, 2)