Changeset: Deprecate `oldLen()` and `newLen()` functions

Eventually all uses of the class will be switched to the generator.

CHANGELOG.md

@@ -36,8 +36,14 @@
     * `opAttributeValue()`
   * `opIterator()`: Deprecated in favor of the new `deserializeOps()` generator
     function.
+  * `opAssembler()`: Deprecated in favor of the new `serializeOps()` function.
+  * `mergingOpAssembler()`: Deprecated in favor of the new `squashOps()`
+    generator function (combined with `serializeOps()`).
+  * `smartOpAssembler()`: Deprecated in favor of the new `canonicalizeOps()`
+    generator function (combined with `serializeOps()`).
   * `appendATextToAssembler()`: Deprecated in favor of the new `opsFromAText()`
     generator function.
+  * `builder()`: Deprecated in favor of the new `Builder` class.
   * `newOp()`: Deprecated in favor of the new `Op` class.
 
 # 1.8.16

src/node/db/API.js

@@ -538,7 +538,7 @@ exports.restoreRevision = async (padID, rev) => {
   };
 
   // create a new changeset with a helper builder object
-  const builder = Changeset.builder(oldText.length);
+  const builder = new Changeset.Builder(oldText.length);
 
   // assemble each line into the builder
   eachAttribRun(atext.attribs, (start, end, attribs) => {

src/node/db/Pad.js

@@ -494,21 +494,20 @@ Pad.prototype.copyPadWithoutHistory = async function (destinationID, force) {
 
   const oldAText = this.atext;
 
-  // based on Changeset.makeSplice
-  const assem = Changeset.smartOpAssembler();
-  for (const op of Changeset.opsFromAText(oldAText)) assem.append(op);
-  assem.endDocument();
+  let newLength;
+  const serializedOps = Changeset.serializeOps((function* () {
+    newLength = yield* Changeset.canonicalizeOps(Changeset.opsFromAText(oldAText), true);
+  })());
 
   // although we have instantiated the newPad with '\n', an additional '\n' is
   // added internally, so the pad text on the revision 0 is "\n\n"
   const oldLength = 2;
 
-  const newLength = assem.getLengthChange();
   const newText = oldAText.text;
 
   // create a changeset that removes the previous text and add the newText with
   // all atributes present on the source pad
-  const changeset = Changeset.pack(oldLength, newLength, assem.toString(), newText);
+  const changeset = Changeset.pack(oldLength, newLength, serializedOps, newText);
   newPad.appendRevision(changeset);
 
   await hooks.aCallAll('padCopy', {originalPad: this, destinationID});

src/node/handler/PadMessageHandler.js

@@ -582,11 +582,10 @@ const handleUserChanges = async (socket, message) => {
     const wireApool = (new AttributePool()).fromJsonable(apool);
     const pad = await padManager.getPad(thisSession.padId);
 
-    // Verify that the changeset has valid syntax and is in canonical form
-    Changeset.checkRep(changeset);
+    const cs = Changeset.unpack(changeset).validate();
 
     // Validate all added 'author' attribs to be the same value as the current user
-    for (const op of Changeset.deserializeOps(Changeset.unpack(changeset).ops)) {
+    for (const op of Changeset.deserializeOps(cs.ops)) {
       // + can add text with attribs
       // = can change or add attribs
       // - can have attribs, but they are discarded and don't show up in the attribs -
@@ -629,10 +628,10 @@ const handleUserChanges = async (socket, message) => {
 
     const prevText = pad.text();
 
-    if (Changeset.oldLen(rebasedChangeset) !== prevText.length) {
+    if (Changeset.unpack(rebasedChangeset).oldLen !== prevText.length) {
       throw new Error(
           `Can't apply changeset ${rebasedChangeset} with oldLen ` +
-          `${Changeset.oldLen(rebasedChangeset)} to document of length ${prevText.length}`);
+          `${Changeset.unpack(rebasedChangeset).oldLen} to document of length ${prevText.length}`);
     }
 
     const newRev = await pad.appendRevision(rebasedChangeset, thisSession.author);
@@ -759,7 +758,7 @@ const _correctMarkersInPad = (atext, apool) => {
   // create changeset that removes these bad markers
   offset = 0;
 
-  const builder = Changeset.builder(text.length);
+  const builder = new Changeset.Builder(text.length);
 
   badMarkers.forEach((pos) => {
     builder.keepText(text.substring(offset, pos));

src/node/utils/ExportHtml.js

@@ -125,7 +125,7 @@ const getHTMLFromAtext = async (pad, atext, authorColors) => {
     // becomes
     // <b>Just bold <i>Bold and italics</i></b> <i>Just italics</i>
     const taker = Changeset.stringIterator(text);
-    const assem = Changeset.stringAssembler();
+    let assem = '';
     const openTags = [];
 
     const getSpanClassFor = (i) => {
@@ -161,16 +161,7 @@ const getHTMLFromAtext = async (pad, atext, authorColors) => {
     const emitOpenTag = (i) => {
       openTags.unshift(i);
       const spanClass = getSpanClassFor(i);
-
-      if (spanClass) {
-        assem.append('<span class="');
-        assem.append(spanClass);
-        assem.append('">');
-      } else {
-        assem.append('<');
-        assem.append(tags[i]);
-        assem.append('>');
-      }
+      assem += spanClass ? `<span class="${spanClass}">` : `<${tags[i]}>`;
     };
 
     // this closes an open tag and removes its reference from openTags
@@ -178,14 +169,7 @@ const getHTMLFromAtext = async (pad, atext, authorColors) => {
       openTags.shift();
       const spanClass = getSpanClassFor(i);
       const spanWithData = isSpanWithData(i);
-
-      if (spanClass || spanWithData) {
-        assem.append('</span>');
-      } else {
-        assem.append('</');
-        assem.append(tags[i]);
-        assem.append('>');
-      }
+      assem += spanClass || spanWithData ? '</span>' : `</${tags[i]}>`;
     };
 
     const urls = padutils.findURLs(text);
@@ -246,7 +230,7 @@ const getHTMLFromAtext = async (pad, atext, authorColors) => {
         // from but they break the abiword parser and are completly useless
         s = s.replace(String.fromCharCode(12), '');
 
-        assem.append(_encodeWhitespace(Security.escapeHTML(s)));
+        assem += _encodeWhitespace(Security.escapeHTML(s));
       } // end iteration over spans in line
 
       // close all the tags that are open after the last op
@@ -269,14 +253,14 @@ const getHTMLFromAtext = async (pad, atext, authorColors) => {
         // https://html.spec.whatwg.org/multipage/links.html#link-type-noopener
         // https://mathiasbynens.github.io/rel-noopener/
         // https://github.com/ether/etherpad-lite/pull/3636
-        assem.append(`<a href="${Security.escapeHTMLAttribute(url)}" rel="noreferrer noopener">`);
+        assem += `<a href="${Security.escapeHTMLAttribute(url)}" rel="noreferrer noopener">`;
         processNextChars(urlLength);
-        assem.append('</a>');
+        assem += '</a>';
       });
     }
     processNextChars(text.length - idx);
 
-    return _processSpaces(assem.toString());
+    return _processSpaces(assem);
   };
   // end getLineHTML
   const pieces = [css];

src/node/utils/ExportTxt.js

@@ -67,7 +67,7 @@ const getTXTFromAtext = (pad, atext, authorColors) => {
     // becomes
     // <b>Just bold <i>Bold and italics</i></b> <i>Just italics</i>
     const taker = Changeset.stringIterator(text);
-    const assem = Changeset.stringAssembler();
+    let assem = '';
 
     let idx = 0;
 
@@ -161,7 +161,7 @@ const getTXTFromAtext = (pad, atext, authorColors) => {
         // plugins from being able to display * at the beginning of a line
         // s = s.replace("*", ""); // Then remove it
 
-        assem.append(s);
+        assem += s;
       } // end iteration over spans in line
 
       const tags2close = [];
@@ -175,7 +175,7 @@ const getTXTFromAtext = (pad, atext, authorColors) => {
     // end processNextChars
 
     processNextChars(text.length - idx);
-    return (assem.toString());
+    return assem;
   };
   // end getLineHTML
 

src/node/utils/ImportHtml.js

@@ -64,7 +64,7 @@ exports.setPadHTML = async (pad, html) => {
   const newAttribs = `${result.lineAttribs.join('|1+1')}|1+1`;
 
   // create a new changeset with a helper builder object
-  const builder = Changeset.builder(1);
+  const builder = new Changeset.Builder(1);
 
   // assemble each line into the builder
   let textIndex = 0;

src/node/utils/padDiff.js

@@ -69,7 +69,7 @@ PadDiff.prototype._createClearAuthorship = async function (rev) {
   const atext = await this._pad.getInternalRevisionAText(rev);
 
   // build clearAuthorship changeset
-  const builder = Changeset.builder(atext.text.length);
+  const builder = new Changeset.Builder(atext.text.length);
   builder.keepText(atext.text, [['author', '']], this._pad.pool);
   const changeset = builder.toString();
 
@@ -206,28 +206,26 @@ PadDiff.prototype._extendChangesetWithAuthor = (changeset, author, apool) => {
   // unpack
   const unpacked = Changeset.unpack(changeset);
 
-  const assem = Changeset.opAssembler();
-
   // create deleted attribs
   const authorAttrib = apool.putAttrib(['author', author || '']);
   const deletedAttrib = apool.putAttrib(['removed', true]);
   const attribs = `*${Changeset.numToString(authorAttrib)}*${Changeset.numToString(deletedAttrib)}`;
 
-  for (const operator of Changeset.deserializeOps(unpacked.ops)) {
-    if (operator.opcode === '-') {
-      // this is a delete operator, extend it with the author
-      operator.attribs = attribs;
-    } else if (operator.opcode === '=' && operator.attribs) {
-      // this is operator changes only attributes, let's mark which author did that
-      operator.attribs += `*${Changeset.numToString(authorAttrib)}`;
+  const serializedOps = Changeset.serializeOps((function* () {
+    for (const operator of Changeset.deserializeOps(unpacked.ops)) {
+      if (operator.opcode === '-') {
+        // this is a delete operator, extend it with the author
+        operator.attribs = attribs;
+      } else if (operator.opcode === '=' && operator.attribs) {
+        // this is operator changes only attributes, let's mark which author did that
+        operator.attribs += `*${Changeset.numToString(authorAttrib)}`;
+      }
+      yield operator;
     }
-
-    // append the new operator to our assembler
-    assem.append(operator);
-  }
+  })());
 
   // return the modified changeset
-  return Changeset.pack(unpacked.oldLen, unpacked.newLen, assem.toString(), unpacked.charBank);
+  return Changeset.pack(unpacked.oldLen, unpacked.newLen, serializedOps, unpacked.charBank);
 };
 
 // this method is 80% like Changeset.inverse. I just changed so instead of reverting,
@@ -264,7 +262,7 @@ PadDiff.prototype._createDeletionChangeset = function (cs, startAText, apool) {
   let curLineNextOp = new Changeset.Op('+');
 
   const unpacked = Changeset.unpack(cs);
-  const builder = Changeset.builder(unpacked.newLen);
+  const builder = new Changeset.Builder(unpacked.newLen);
 
   const consumeAttribRuns = (numChars, func /* (len, attribs, endsLine)*/) => {
     if (!curLineOps || curLineOpsLine !== curLine) {
@@ -330,21 +328,21 @@ PadDiff.prototype._createDeletionChangeset = function (cs, startAText, apool) {
 
   const nextText = (numChars) => {
     let len = 0;
-    const assem = Changeset.stringAssembler();
+    let assem = '';
     const firstString = linesGet(curLine).substring(curChar);
     len += firstString.length;
-    assem.append(firstString);
+    assem += firstString;
 
     let lineNum = curLine + 1;
 
     while (len < numChars) {
       const nextString = linesGet(lineNum);
       len += nextString.length;
-      assem.append(nextString);
+      assem += nextString;
       lineNum++;
     }
 
-    return assem.toString().substring(0, numChars);
+    return assem.substring(0, numChars);
   };
 
   const cachedStrFunc = (func) => {
@@ -440,7 +438,7 @@ PadDiff.prototype._createDeletionChangeset = function (cs, startAText, apool) {
     }
   }
 
-  return Changeset.checkRep(builder.toString());
+  return builder.build().validate().toString();
 };
 
 // export the constructor

src/static/js/AttributeManager.js

@@ -125,7 +125,7 @@ AttributeManager.prototype = _(AttributeManager.prototype).extend({
    * @param attribs an array of attributes
    */
   _setAttributesOnRangeByLine(row, startCol, endCol, attribs) {
-    const builder = Changeset.builder(this.rep.lines.totalWidth());
+    const builder = new Changeset.Builder(this.rep.lines.totalWidth());
     ChangesetUtils.buildKeepToStartOfRange(this.rep, builder, [row, startCol]);
     ChangesetUtils.buildKeepRange(
         this.rep, builder, [row, startCol], [row, endCol], attribs, this.rep.apool);
@@ -285,7 +285,7 @@ AttributeManager.prototype = _(AttributeManager.prototype).extend({
   */
   setAttributeOnLine(lineNum, attributeName, attributeValue) {
     let loc = [0, 0];
-    const builder = Changeset.builder(this.rep.lines.totalWidth());
+    const builder = new Changeset.Builder(this.rep.lines.totalWidth());
     const hasMarker = this.lineHasMarker(lineNum);
 
     ChangesetUtils.buildKeepRange(this.rep, builder, loc, (loc = [lineNum, 0]));
@@ -314,7 +314,7 @@ AttributeManager.prototype = _(AttributeManager.prototype).extend({
    *  @param attributeValue if given only attributes with equal value will be removed
    */
   removeAttributeOnLine(lineNum, attributeName, attributeValue) {
-    const builder = Changeset.builder(this.rep.lines.totalWidth());
+    const builder = new Changeset.Builder(this.rep.lines.totalWidth());
     const hasMarker = this.lineHasMarker(lineNum);
     let found = false;
 

src/static/js/ace2_inner.js

@@ -170,7 +170,7 @@ function Ace2Inner(editorInfo, cssManagers) {
     //           CCCCCCCCCCCCCCCCCCCC\n
     //           CCCC\n
     // end[0]:   <CCC end[1] CCC>-------\n
-    const builder = Changeset.builder(rep.lines.totalWidth());
+    const builder = new Changeset.Builder(rep.lines.totalWidth());
     ChangesetUtils.buildKeepToStartOfRange(rep, builder, start);
     ChangesetUtils.buildRemoveRange(rep, builder, start, end);
     builder.insert(newText, [
@@ -522,18 +522,24 @@ function Ace2Inner(editorInfo, cssManagers) {
     const numLines = rep.lines.length();
     const upToLastLine = rep.lines.offsetOfIndex(numLines - 1);
     const lastLineLength = rep.lines.atIndex(numLines - 1).text.length;
-    const assem = Changeset.smartOpAssembler();
-    const o = new Changeset.Op('-');
-    o.chars = upToLastLine;
-    o.lines = numLines - 1;
-    assem.append(o);
-    o.chars = lastLineLength;
-    o.lines = 0;
-    assem.append(o);
-    for (const op of Changeset.opsFromAText(atext)) assem.append(op);
-    const newLen = oldLen + assem.getLengthChange();
-    const changeset = Changeset.checkRep(
-        Changeset.pack(oldLen, newLen, assem.toString(), atext.text.slice(0, -1)));
+    const ops = (function* () {
+      const op1 = new Changeset.Op('-');
+      op1.chars = upToLastLine;
+      op1.lines = numLines - 1;
+      yield op1;
+      const op2 = new Changeset.Op('-');
+      op2.chars = lastLineLength;
+      op2.lines = 0;
+      yield op2;
+      yield* Changeset.opsFromAText(atext);
+    })();
+    let lengthChange;
+    const serializedOps = Changeset.serializeOps((function* () {
+      lengthChange = yield* Changeset.canonicalizeOps(ops, false);
+    })());
+    const newLen = oldLen + lengthChange;
+    const changeset = Changeset.pack(oldLen, newLen, serializedOps, atext.text.slice(0, -1));
+    Changeset.unpack(changeset).validate();
     performDocumentApplyChangeset(changeset);
 
     performSelectionChange(
@@ -1266,7 +1272,7 @@ function Ace2Inner(editorInfo, cssManagers) {
       if (shouldIndent && /[[(:{]\s*$/.exec(prevLineText)) {
         theIndent += THE_TAB;
       }
-      const cs = Changeset.builder(rep.lines.totalWidth()).keep(
+      const cs = new Changeset.Builder(rep.lines.totalWidth()).keep(
           rep.lines.offsetOfIndex(lineNum), lineNum).insert(
           theIndent, [
             ['author', thisAuthor],
@@ -1441,11 +1447,10 @@ function Ace2Inner(editorInfo, cssManagers) {
   };
 
   const doRepApplyChangeset = (changes, insertsAfterSelection) => {
-    Changeset.checkRep(changes);
+    const cs = Changeset.unpack(changes).validate();
 
-    if (Changeset.oldLen(changes) !== rep.alltext.length) {
-      const errMsg = `${Changeset.oldLen(changes)}/${rep.alltext.length}`;
-      throw new Error(`doRepApplyChangeset length mismatch: ${errMsg}`);
+    if (cs.oldLen !== rep.alltext.length) {
+      throw new Error(`doRepApplyChangeset length mismatch: ${cs.oldLen}/${rep.alltext.length}`);
     }
 
     const editEvent = currentCallStack.editEvent;
@@ -1740,7 +1745,7 @@ function Ace2Inner(editorInfo, cssManagers) {
       const spliceStartLineStart = rep.lines.offsetOfIndex(spliceStartLine);
 
       const startBuilder = () => {
-        const builder = Changeset.builder(oldLen);
+        const builder = new Changeset.Builder(oldLen);
         builder.keep(spliceStartLineStart, spliceStartLine);
         builder.keep(spliceStart - spliceStartLineStart);
         return builder;
@@ -2291,7 +2296,7 @@ function Ace2Inner(editorInfo, cssManagers) {
 
     // 3-renumber every list item of the same level from the beginning, level 1
     // IMPORTANT: never skip a level because there imbrication may be arbitrary
-    const builder = Changeset.builder(rep.lines.totalWidth());
+    const builder = new Changeset.Builder(rep.lines.totalWidth());
     let loc = [0, 0];
     const applyNumberList = (line, level) => {
       // init

src/static/js/changesettracker.js

@@ -143,22 +143,22 @@ const makeChangesetTracker = (scheduler, apool, aceCallbacksProvider) => {
         // Sanitize authorship: Replace all author attributes with this user's author ID in case the
         // text was copied from another author.
         const cs = Changeset.unpack(userChangeset);
-        const assem = Changeset.mergingOpAssembler();
-
-        for (const op of Changeset.deserializeOps(cs.ops)) {
-          if (op.opcode === '+') {
-            const attribs = AttributeMap.fromString(op.attribs, apool);
-            const oldAuthorId = attribs.get('author');
-            if (oldAuthorId != null && oldAuthorId !== authorId) {
-              attribs.set('author', authorId);
-              op.attribs = attribs.toString();
+        const ops = (function* () {
+          for (const op of Changeset.deserializeOps(cs.ops)) {
+            if (op.opcode === '+') {
+              const attribs = AttributeMap.fromString(op.attribs, apool);
+              const oldAuthorId = attribs.get('author');
+              if (oldAuthorId != null && oldAuthorId !== authorId) {
+                attribs.set('author', authorId);
+                op.attribs = attribs.toString();
+              }
             }
+            yield op;
           }
-          assem.append(op);
-        }
-        assem.endDocument();
-        userChangeset = Changeset.pack(cs.oldLen, cs.newLen, assem.toString(), cs.charBank);
-        Changeset.checkRep(userChangeset);
+        })();
+        const serializedOps = Changeset.serializeOps(Changeset.squashOps(ops, true));
+        userChangeset = Changeset.pack(cs.oldLen, cs.newLen, serializedOps, cs.charBank);
+        Changeset.unpack(userChangeset).validate();
 
         if (Changeset.isIdentity(userChangeset)) toSubmit = null;
         else toSubmit = userChangeset;
@@ -167,7 +167,7 @@ const makeChangesetTracker = (scheduler, apool, aceCallbacksProvider) => {
       let cs = null;
       if (toSubmit) {
         submittedChangeset = toSubmit;
-        userChangeset = Changeset.identity(Changeset.newLen(toSubmit));
+        userChangeset = Changeset.identity(Changeset.unpack(toSubmit).newLen);
 
         cs = toSubmit;
       }

src/static/js/contentcollector.js

@@ -82,31 +82,30 @@ const makeContentCollector = (collectStyles, abrowser, apool, className2Author)
   const lines = (() => {
     const textArray = [];
     const attribsArray = [];
-    let attribsBuilder = null;
-    const op = new Changeset.Op('+');
+    let ops = null;
     const self = {
       length: () => textArray.length,
       atColumnZero: () => textArray[textArray.length - 1] === '',
       startNew: () => {
         textArray.push('');
         self.flush(true);
-        attribsBuilder = Changeset.smartOpAssembler();
+        ops = [];
       },
       textOfLine: (i) => textArray[i],
       appendText: (txt, attrString = '') => {
         textArray[textArray.length - 1] += txt;
+        const op = new Changeset.Op('+');
         op.attribs = attrString;
         op.chars = txt.length;
-        attribsBuilder.append(op);
+        ops.push(op);
       },
       textLines: () => textArray.slice(),
       attribLines: () => attribsArray,
       // call flush only when you're done
       flush: (withNewline) => {
-        if (attribsBuilder) {
-          attribsArray.push(attribsBuilder.toString());
-          attribsBuilder = null;
-        }
+        if (ops == null) return;
+        attribsArray.push(Changeset.serializeOps(Changeset.canonicalizeOps(ops, false)));
+        ops = null;
       },
     };
     self.startNew();

src/tests/frontend/easysync-helper.js

@@ -20,29 +20,19 @@ const poolOrArray = (attribs) => {
 exports.poolOrArray = poolOrArray;
 
 const randomInlineString = (len) => {
-  const assem = Changeset.stringAssembler();
-  for (let i = 0; i < len; i++) {
-    assem.append(String.fromCharCode(randInt(26) + 97));
-  }
-  return assem.toString();
+  let assem = '';
+  for (let i = 0; i < len; i++) assem += String.fromCharCode(randInt(26) + 97);
+  return assem;
 };
 
 const randomMultiline = (approxMaxLines, approxMaxCols) => {
   const numParts = randInt(approxMaxLines * 2) + 1;
-  const txt = Changeset.stringAssembler();
-  txt.append(randInt(2) ? '\n' : '');
+  let txt = '';
+  txt += randInt(2) ? '\n' : '';
   for (let i = 0; i < numParts; i++) {
-    if ((i % 2) === 0) {
-      if (randInt(10)) {
-        txt.append(randomInlineString(randInt(approxMaxCols) + 1));
-      } else {
-        txt.append('\n');
-      }
-    } else {
-      txt.append('\n');
-    }
+    txt += i % 2 === 0 && randInt(10) ? randomInlineString(randInt(approxMaxCols) + 1) : '\n';
   }
-  return txt.toString();
+  return txt;
 };
 exports.randomMultiline = randomMultiline;
 
@@ -165,29 +155,25 @@ const randomTwoPropAttribs = (opcode) => {
 };
 
 const randomTestChangeset = (origText, withAttribs) => {
-  const charBank = Changeset.stringAssembler();
+  let charBank = '';
   let textLeft = origText; // always keep final newline
-  const outTextAssem = Changeset.stringAssembler();
-  const opAssem = Changeset.smartOpAssembler();
+  let outTextAssem = '';
+  const ops = [];
   const oldLen = origText.length;
 
-  const nextOp = new Changeset.Op();
-
   const appendMultilineOp = (opcode, txt) => {
-    nextOp.opcode = opcode;
-    if (withAttribs) {
-      nextOp.attribs = randomTwoPropAttribs(opcode);
-    }
+    const attribs = withAttribs ? randomTwoPropAttribs(opcode) : '';
     txt.replace(/\n|[^\n]+/g, (t) => {
+      const nextOp = new Changeset.Op(opcode);
+      nextOp.attribs = attribs;
       if (t === '\n') {
         nextOp.chars = 1;
         nextOp.lines = 1;
-        opAssem.append(nextOp);
       } else {
         nextOp.chars = t.length;
         nextOp.lines = 0;
-        opAssem.append(nextOp);
       }
+      ops.push(nextOp);
       return '';
     });
   };
@@ -196,13 +182,13 @@ const randomTestChangeset = (origText, withAttribs) => {
     const o = randomStringOperation(textLeft.length);
     if (o.insert) {
       const txt = o.insert;
-      charBank.append(txt);
-      outTextAssem.append(txt);
+      charBank += txt;
+      outTextAssem += txt;
       appendMultilineOp('+', txt);
     } else if (o.skip) {
       const txt = textLeft.substring(0, o.skip);
       textLeft = textLeft.substring(o.skip);
-      outTextAssem.append(txt);
+      outTextAssem += txt;
       appendMultilineOp('=', txt);
     } else if (o.remove) {
       const txt = textLeft.substring(0, o.remove);
@@ -213,10 +199,10 @@ const randomTestChangeset = (origText, withAttribs) => {
 
   while (textLeft.length > 1) doOp();
   for (let i = 0; i < 5; i++) doOp(); // do some more (only insertions will happen)
-  const outText = `${outTextAssem.toString()}\n`;
-  opAssem.endDocument();
-  const cs = Changeset.pack(oldLen, outText.length, opAssem.toString(), charBank.toString());
-  Changeset.checkRep(cs);
+  const outText = `${outTextAssem}\n`;
+  const serializedOps = Changeset.serializeOps(Changeset.canonicalizeOps(ops, true));
+  const cs = Changeset.pack(oldLen, outText.length, serializedOps, charBank);
+  Changeset.unpack(cs).validate();
   return [cs, outText];
 };
 exports.randomTestChangeset = randomTestChangeset;

src/tests/frontend/specs/easysync-assembler.js

@@ -3,27 +3,23 @@
 const Changeset = require('../../../static/js/Changeset');
 
 describe('easysync-assembler', function () {
-  it('opAssembler', async function () {
+  it('deserialize and serialize', async function () {
     const x = '-c*3*4+6|3=az*asdf0*1*2*3+1=1-1+1*0+1=1-1+1|c=c-1';
-    const assem = Changeset.opAssembler();
-    for (const op of Changeset.deserializeOps(x)) assem.append(op);
-    expect(assem.toString()).to.equal(x);
+    expect(Changeset.serializeOps(Changeset.deserializeOps(x))).to.equal(x);
   });
 
-  it('smartOpAssembler', async function () {
+  it('canonicalizeOps', async function () {
     const x = '-c*3*4+6|3=az*asdf0*1*2*3+1=1-1+1*0+1=1-1+1|c=c-1';
-    const assem = Changeset.smartOpAssembler();
-    for (const op of Changeset.deserializeOps(x)) assem.append(op);
-    assem.endDocument();
-    expect(assem.toString()).to.equal(x);
+    expect(Changeset.serializeOps(Changeset.canonicalizeOps(Changeset.deserializeOps(x), true)))
+        .to.equal(x);
   });
 
   describe('append atext to assembler', function () {
     const testAppendATextToAssembler = (testId, atext, correctOps) => {
       it(`testAppendATextToAssembler#${testId}`, async function () {
-        const assem = Changeset.smartOpAssembler();
-        for (const op of Changeset.opsFromAText(atext)) assem.append(op);
-        expect(assem.toString()).to.equal(correctOps);
+        const serializedOps =
+            Changeset.serializeOps(Changeset.canonicalizeOps(Changeset.opsFromAText(atext), false));
+        expect(serializedOps).to.equal(correctOps);
       });
     };
 

src/tests/frontend/specs/easysync-compose.js

@@ -24,10 +24,14 @@ describe('easysync-compose', function () {
         const change3 = x3[0];
         const text3 = x3[1];
 
-        const change12 = Changeset.checkRep(Changeset.compose(change1, change2, p));
-        const change23 = Changeset.checkRep(Changeset.compose(change2, change3, p));
-        const change123 = Changeset.checkRep(Changeset.compose(change12, change3, p));
-        const change123a = Changeset.checkRep(Changeset.compose(change1, change23, p));
+        const change12 = Changeset.compose(change1, change2, p);
+        Changeset.unpack(change12).validate();
+        const change23 = Changeset.compose(change2, change3, p);
+        Changeset.unpack(change23).validate();
+        const change123 = Changeset.compose(change12, change3, p);
+        Changeset.unpack(change123).validate();
+        const change123a = Changeset.compose(change1, change23, p);
+        Changeset.unpack(change123a).validate();
         expect(change123a).to.equal(change123);
 
         expect(Changeset.applyToText(change12, startText)).to.equal(text2);
@@ -44,9 +48,12 @@ describe('easysync-compose', function () {
       const p = new AttributePool();
       p.putAttrib(['bold', '']);
       p.putAttrib(['bold', 'true']);
-      const cs1 = Changeset.checkRep('Z:2>1*1+1*1=1$x');
-      const cs2 = Changeset.checkRep('Z:3>0*0|1=3$');
-      const cs12 = Changeset.checkRep(Changeset.compose(cs1, cs2, p));
+      const cs1 = 'Z:2>1*1+1*1=1$x';
+      Changeset.unpack(cs1).validate();
+      const cs2 = 'Z:3>0*0|1=3$';
+      Changeset.unpack(cs2).validate();
+      const cs12 = Changeset.compose(cs1, cs2, p);
+      Changeset.unpack(cs12).validate();
       expect(cs12).to.equal('Z:2>1+1*0|1=2$x');
     });
   });

src/tests/frontend/specs/easysync-follow.js

@@ -15,11 +15,15 @@ describe('easysync-follow', function () {
         const cs1 = randomTestChangeset(startText)[0];
         const cs2 = randomTestChangeset(startText)[0];
 
-        const afb = Changeset.checkRep(Changeset.follow(cs1, cs2, false, p));
-        const bfa = Changeset.checkRep(Changeset.follow(cs2, cs1, true, p));
+        const afb = Changeset.follow(cs1, cs2, false, p);
+        Changeset.unpack(afb).validate();
+        const bfa = Changeset.follow(cs2, cs1, true, p);
+        Changeset.unpack(bfa).validate();
 
-        const merge1 = Changeset.checkRep(Changeset.compose(cs1, afb));
-        const merge2 = Changeset.checkRep(Changeset.compose(cs2, bfa));
+        const merge1 = Changeset.compose(cs1, afb);
+        Changeset.unpack(merge1).validate();
+        const merge2 = Changeset.compose(cs2, bfa);
+        Changeset.unpack(merge2).validate();
 
         expect(merge2).to.equal(merge1);
       });
@@ -60,7 +64,7 @@ describe('easysync-follow', function () {
   describe('chracterRangeFollow', function () {
     const testCharacterRangeFollow = (testId, cs, oldRange, insertionsAfter, correctNewRange) => {
       it(`testCharacterRangeFollow#${testId}`, async function () {
-        cs = Changeset.checkRep(cs);
+        Changeset.unpack(cs).validate();
         expect(Changeset.characterRangeFollow(cs, oldRange[0], oldRange[1], insertionsAfter))
             .to.eql(correctNewRange);
       });

src/tests/frontend/specs/easysync-inverseRandom.js

@@ -41,7 +41,8 @@ describe('easysync-inverseRandom', function () {
     const testInverse = (testId, cs, lines, alines, pool, correctOutput) => {
       it(`testInverse#${testId}`, async function () {
         pool = poolOrArray(pool);
-        const str = Changeset.inverse(Changeset.checkRep(cs), lines, alines, pool);
+        Changeset.unpack(cs).validate();
+        const str = Changeset.inverse(cs, lines, alines, pool);
         expect(str).to.equal(correctOutput);
       });
     };

src/tests/frontend/specs/easysync-mutations.js

@@ -15,37 +15,36 @@ describe('easysync-mutations', function () {
   };
 
   const mutationsToChangeset = (oldLen, arrayOfArrays) => {
-    const assem = Changeset.smartOpAssembler();
-    const op = new Changeset.Op();
-    const bank = Changeset.stringAssembler();
+    let bank = '';
     let oldPos = 0;
     let newLen = 0;
-    arrayOfArrays.forEach((a) => {
-      if (a[0] === 'skip') {
-        op.opcode = '=';
-        op.chars = a[1];
-        op.lines = (a[2] || 0);
-        assem.append(op);
-        oldPos += op.chars;
-        newLen += op.chars;
-      } else if (a[0] === 'remove') {
-        op.opcode = '-';
-        op.chars = a[1];
-        op.lines = (a[2] || 0);
-        assem.append(op);
-        oldPos += op.chars;
-      } else if (a[0] === 'insert') {
-        op.opcode = '+';
-        bank.append(a[1]);
-        op.chars = a[1].length;
-        op.lines = (a[2] || 0);
-        assem.append(op);
-        newLen += op.chars;
+    const ops = (function* () {
+      for (const a of arrayOfArrays) {
+        const op = new Changeset.Op();
+        if (a[0] === 'skip') {
+          op.opcode = '=';
+          op.chars = a[1];
+          op.lines = (a[2] || 0);
+          oldPos += op.chars;
+          newLen += op.chars;
+        } else if (a[0] === 'remove') {
+          op.opcode = '-';
+          op.chars = a[1];
+          op.lines = (a[2] || 0);
+          oldPos += op.chars;
+        } else if (a[0] === 'insert') {
+          op.opcode = '+';
+          bank += a[1];
+          op.chars = a[1].length;
+          op.lines = (a[2] || 0);
+          newLen += op.chars;
+        }
+        yield op;
       }
-    });
+    })();
+    const serializedOps = Changeset.serializeOps(Changeset.canonicalizeOps(ops, true));
     newLen += oldLen - oldPos;
-    assem.endDocument();
-    return Changeset.pack(oldLen, newLen, assem.toString(), bank.toString());
+    return Changeset.pack(oldLen, newLen, serializedOps, bank);
   };
 
   const runMutationTest = (testId, origLines, muts, correct) => {
@@ -205,7 +204,8 @@ describe('easysync-mutations', function () {
       it(`runMutateAttributionTest#${testId}`, async function () {
         const p = poolOrArray(attribs);
         const alines2 = Array.prototype.slice.call(alines);
-        Changeset.mutateAttributionLines(Changeset.checkRep(cs), alines2, p);
+        Changeset.unpack(cs).validate();
+        Changeset.mutateAttributionLines(cs, alines2, p);
         expect(alines2).to.eql(outCorrect);
 
         const removeQuestionMarks = (a) => a.replace(/\?/g, '');

src/tests/frontend/specs/easysync-other.js

@@ -78,7 +78,8 @@ describe('easysync-other', function () {
     });
 
     it('testToSplices', async function () {
-      const cs = Changeset.checkRep('Z:z>9*0=1=4-3+9=1|1-4-4+1*0+a$123456789abcdefghijk');
+      const cs = 'Z:z>9*0=1=4-3+9=1|1-4-4+1*0+a$123456789abcdefghijk';
+      Changeset.unpack(cs).validate();
       const correctSplices = [
         [5, 8, '123456789'],
         [9, 17, 'abcdefghijk'],
@@ -112,7 +113,8 @@ describe('easysync-other', function () {
       const runApplyToAttributionTest = (testId, attribs, cs, inAttr, outCorrect) => {
         it(`applyToAttribution#${testId}`, async function () {
           const p = poolOrArray(attribs);
-          const result = Changeset.applyToAttribution(Changeset.checkRep(cs), inAttr, p);
+          Changeset.unpack(cs).validate();
+          const result = Changeset.applyToAttribution(cs, inAttr, p);
           expect(result).to.equal(outCorrect);
         });
       };
@@ -129,16 +131,17 @@ describe('easysync-other', function () {
     describe('split/join attribution lines', function () {
       const testSplitJoinAttributionLines = (randomSeed) => {
         const stringToOps = (str) => {
-          const assem = Changeset.mergingOpAssembler();
-          const o = new Changeset.Op('+');
-          o.chars = 1;
-          for (let i = 0; i < str.length; i++) {
-            const c = str.charAt(i);
-            o.lines = (c === '\n' ? 1 : 0);
-            o.attribs = (c === 'a' || c === 'b' ? `*${c}` : '');
-            assem.append(o);
-          }
-          return assem.toString();
+          const ops = (function* () {
+            for (let i = 0; i < str.length; i++) {
+              const c = str.charAt(i);
+              const o = new Changeset.Op('+');
+              o.chars = 1;
+              o.lines = (c === '\n' ? 1 : 0);
+              o.attribs = (c === 'a' || c === 'b' ? `*${c}` : '');
+              yield o;
+            }
+          })();
+          return Changeset.serializeOps(Changeset.squashOps(ops, false));
         };
 
         it(`testSplitJoinAttributionLines#${randomSeed}`, async function () {