angular · jessicajaniuk · Nov 7, 2023
diff --git a/packages/core/schematics/ng-generate/control-flow-migration/fors.ts b/packages/core/schematics/ng-generate/control-flow-migration/fors.ts
@@ -0,0 +1,181 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {visitAll} from '@angular/compiler';
+
+import {ElementCollector, ElementToMigrate, MigrateError, Result} from './types';
+import {calculateNesting, getMainBlock, getOriginals, hasLineBreaks, parseTemplate, reduceNestingOffset} from './util';
+
+export const ngfor = '*ngFor';
+export const commaSeparatedSyntax = new Map([
+  ['(', ')'],
+  ['{', '}'],
+  ['[', ']'],
+]);
+export const stringPairs = new Map([
+  [`"`, `"`],
+  [`'`, `'`],
+]);
+
+/**
+ * Replaces structural directive ngFor instances with new for.
+ * Returns null if the migration failed (e.g. there was a syntax error).
+ */
+export function migrateFor(template: string): {migrated: string, errors: MigrateError[]} {
+  let errors: MigrateError[] = [];
+  let parsed = parseTemplate(template);
+  if (parsed === null) {
+    return {migrated: template, errors};
+  }
+
+  let result = template;
+  const visitor = new ElementCollector([ngfor]);
+  visitAll(visitor, parsed.rootNodes);
+  calculateNesting(visitor, hasLineBreaks(template));
+
+  // this tracks the character shift from different lengths of blocks from
+  // the prior directives so as to adjust for nested block replacement during
+  // migration. Each block calculates length differences and passes that offset
+  // to the next migrating block to adjust character offsets properly.
+  let offset = 0;
+  let nestLevel = -1;
+  let postOffsets: number[] = [];
+  for (const el of visitor.elements) {
+    let migrateResult: Result = {tmpl: result, offsets: {pre: 0, post: 0}};
+    // applies the post offsets after closing
+    offset = reduceNestingOffset(el, nestLevel, offset, postOffsets);
+
+    try {
+      migrateResult = migrateNgFor(el, result, offset);
+    } catch (error: unknown) {
+      errors.push({type: ngfor, error});
+    }
+
+    result = migrateResult.tmpl;
+    offset += migrateResult.offsets.pre;
+    postOffsets.push(migrateResult.offsets.post);
+    nestLevel = el.nestCount;
+  }
+
+  return {migrated: result, errors};
+}
+
+
+function migrateNgFor(etm: ElementToMigrate, tmpl: string, offset: number): Result {
+  const aliasWithEqualRegexp = /=\s*(count|index|first|last|even|odd)/gm;
+  const aliasWithAsRegexp = /(count|index|first|last|even|odd)\s+as/gm;
+  const aliases = [];
+  const lbString = etm.hasLineBreaks ? '\n' : '';
+  const lbSpaces = etm.hasLineBreaks ? `\n  ` : '';
+  const parts = getNgForParts(etm.attr.value);
+
+  const originals = getOriginals(etm, tmpl, offset);
+
+  // first portion should always be the loop definition prefixed with `let`
+  const condition = parts[0].replace('let ', '');
+  const loopVar = condition.split(' of ')[0];
+  let trackBy = loopVar;
+  let aliasedIndex: string|null = null;
+  for (let i = 1; i < parts.length; i++) {
+    const part = parts[i].trim();
+
+    if (part.startsWith('trackBy:')) {
+      // build trackby value
+      const trackByFn = part.replace('trackBy:', '').trim();
+      trackBy = `${trackByFn}($index, ${loopVar})`;
+    }
+    // aliases
+    // declared with `let myIndex = index`
+    if (part.match(aliasWithEqualRegexp)) {
+      // 'let myIndex = index' -> ['let myIndex', 'index']
+      const aliasParts = part.split('=');
+      // -> 'let myIndex = $index'
+      aliases.push(` ${aliasParts[0].trim()} = $${aliasParts[1].trim()}`);
+      // if the aliased variable is the index, then we store it
+      if (aliasParts[1].trim() === 'index') {
+        // 'let myIndex' -> 'myIndex'
+        aliasedIndex = aliasParts[0].replace('let', '').trim();
+      }
+    }
+    // declared with `index as myIndex`
+    if (part.match(aliasWithAsRegexp)) {
+      // 'index    as   myIndex' -> ['index', 'myIndex']
+      const aliasParts = part.split(/\s+as\s+/);
+      // -> 'let myIndex = $index'
+      aliases.push(` let ${aliasParts[1].trim()} = $${aliasParts[0].trim()}`);
+      // if the aliased variable is the index, then we store it
+      if (aliasParts[0].trim() === 'index') {
+        aliasedIndex = aliasParts[1].trim();
+      }
+    }
+  }
+  // if an alias has been defined for the index, then the trackBy function must use it
+  if (aliasedIndex !== null && trackBy !== loopVar) {
+    // byId($index, user) -> byId(i, user)
+    trackBy = trackBy.replace('$index', aliasedIndex);
+  }
+
+  const aliasStr = (aliases.length > 0) ? `;${aliases.join(';')}` : '';
+
+  const {start, middle, end} = getMainBlock(etm, tmpl, offset);
+  const startBlock = `@for (${condition}; track ${trackBy}${aliasStr}) {${lbSpaces}${start}`;
+
+  const endBlock = `${end}${lbString}}`;
+  const forBlock = startBlock + middle + endBlock;
+
+  const updatedTmpl = tmpl.slice(0, etm.start(offset)) + forBlock + tmpl.slice(etm.end(offset));
+
+  const pre = originals.start.length - startBlock.length;
+  const post = originals.end.length - endBlock.length;
+
+  return {tmpl: updatedTmpl, offsets: {pre, post}};
+}
+
+function getNgForParts(expression: string): string[] {
+  const parts: string[] = [];
+  const commaSeparatedStack: string[] = [];
+  const stringStack: string[] = [];
+  let current = '';
+
+  for (let i = 0; i < expression.length; i++) {
+    const char = expression[i];
+    const isInString = stringStack.length === 0;
+    const isInCommaSeparated = commaSeparatedStack.length === 0;
+
+    // Any semicolon is a delimiter, as well as any comma outside
+    // of comma-separated syntax, as long as they're outside of a string.
+    if (isInString && current.length > 0 &&
+        (char === ';' || (char === ',' && isInCommaSeparated))) {
+      parts.push(current);
+      current = '';
+      continue;
+    }
+
+    if (stringPairs.has(char)) {
+      stringStack.push(stringPairs.get(char)!);
+    } else if (stringStack.length > 0 && stringStack[stringStack.length - 1] === char) {
+      stringStack.pop();
+    }
+
+    if (commaSeparatedSyntax.has(char)) {
+      commaSeparatedStack.push(commaSeparatedSyntax.get(char)!);
+    } else if (
+        commaSeparatedStack.length > 0 &&
+        commaSeparatedStack[commaSeparatedStack.length - 1] === char) {
+      commaSeparatedStack.pop();
+    }
+
+    current += char;
+  }
+
+  if (current.length > 0) {
+    parts.push(current);
+  }
+
+  return parts;
+}
diff --git a/packages/core/schematics/ng-generate/control-flow-migration/ifs.ts b/packages/core/schematics/ng-generate/control-flow-migration/ifs.ts
@@ -0,0 +1,156 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {visitAll} from '@angular/compiler';
+
+import {ElementCollector, ElementToMigrate, MigrateError, Result} from './types';
+import {calculateNesting, getMainBlock, getOriginals, hasLineBreaks, parseTemplate, reduceNestingOffset} from './util';
+
+export const ngif = '*ngIf';
+export const boundngif = '[ngIf]';
+export const nakedngif = 'ngIf';
+
+export const ifs = [
+  ngif,
+  nakedngif,
+  boundngif,
+];
+
+/**
+ * Replaces structural directive ngif instances with new if.
+ * Returns null if the migration failed (e.g. there was a syntax error).
+ */
+export function migrateIf(template: string): {migrated: string, errors: MigrateError[]} {
+  let errors: MigrateError[] = [];
+  let parsed = parseTemplate(template);
+  if (parsed === null) {
+    return {migrated: template, errors};
+  }
+
+  let result = template;
+  const visitor = new ElementCollector(ifs);
+  visitAll(visitor, parsed.rootNodes);
+  calculateNesting(visitor, hasLineBreaks(template));
+
+  // this tracks the character shift from different lengths of blocks from
+  // the prior directives so as to adjust for nested block replacement during
+  // migration. Each block calculates length differences and passes that offset
+  // to the next migrating block to adjust character offsets properly.
+  let offset = 0;
+  let nestLevel = -1;
+  let postOffsets: number[] = [];
+  for (const el of visitor.elements) {
+    let migrateResult: Result = {tmpl: result, offsets: {pre: 0, post: 0}};
+    // applies the post offsets after closing
+    offset = reduceNestingOffset(el, nestLevel, offset, postOffsets);
+
+    try {
+      migrateResult = migrateNgIf(el, result, offset);
+    } catch (error: unknown) {
+      errors.push({type: ngif, error});
+    }
+
+    result = migrateResult.tmpl;
+    offset += migrateResult.offsets.pre;
+    postOffsets.push(migrateResult.offsets.post);
+    nestLevel = el.nestCount;
+  }
+
+  return {migrated: result, errors};
+}
+
+export function migrateNgIf(etm: ElementToMigrate, tmpl: string, offset: number): Result {
+  const matchThen = etm.attr.value.match(/;\s*then/gm);
+  const matchElse = etm.attr.value.match(/;\s*else/gm);
+
+  if (matchThen && matchThen.length > 0) {
+    return buildIfThenElseBlock(etm, tmpl, matchThen[0], matchElse![0], offset);
+  } else if (matchElse && matchElse.length > 0) {
+    // just else
+    return buildIfElseBlock(etm, tmpl, matchElse[0], offset);
+  }
+
+  return buildIfBlock(etm, tmpl, offset);
+}
+
+function buildIfBlock(etm: ElementToMigrate, tmpl: string, offset: number): Result {
+  // includes the mandatory semicolon before as
+  const lbString = etm.hasLineBreaks ? '\n' : '';
+  const condition = etm.attr.value.replace(' as ', '; as ');
+
+  const originals = getOriginals(etm, tmpl, offset);
+
+  const {start, middle, end} = getMainBlock(etm, tmpl, offset);
+  const startBlock = `@if (${condition}) {${lbString}${start}`;
+  const endBlock = `${end}${lbString}}`;
+
+  const ifBlock = startBlock + middle + endBlock;
+  const updatedTmpl = tmpl.slice(0, etm.start(offset)) + ifBlock + tmpl.slice(etm.end(offset));
+
+  // this should be the difference between the starting element up to the start of the closing
+  // element and the mainblock sans }
+  const pre = originals.start.length - startBlock.length;
+  const post = originals.end.length - endBlock.length;
+
+  return {tmpl: updatedTmpl, offsets: {pre, post}};
+}
+
+function buildIfElseBlock(
+    etm: ElementToMigrate, tmpl: string, elseString: string, offset: number): Result {
+  // includes the mandatory semicolon before as
+  const lbString = etm.hasLineBreaks ? '\n' : '';
+  const condition = etm.getCondition(elseString).replace(' as ', '; as ');
+
+  const originals = getOriginals(etm, tmpl, offset);
+
+  const elsePlaceholder = `#${etm.getTemplateName(elseString)}|`;
+  const {start, middle, end} = getMainBlock(etm, tmpl, offset);
+  const startBlock = `@if (${condition}) {${lbString}${start}`;
+
+  const elseBlock = `${end}${lbString}} @else {${lbString}`;
+
+  const postBlock = elseBlock + elsePlaceholder + `${lbString}}`;
+  const ifElseBlock = startBlock + middle + postBlock;
+
+  const tmplStart = tmpl.slice(0, etm.start(offset));
+  const tmplEnd = tmpl.slice(etm.end(offset));
+  const updatedTmpl = tmplStart + ifElseBlock + tmplEnd;
+
+  const pre = originals.start.length - startBlock.length;
+  const post = originals.end.length - postBlock.length;
+
+  return {tmpl: updatedTmpl, offsets: {pre, post}};
+}
+
+function buildIfThenElseBlock(
+    etm: ElementToMigrate, tmpl: string, thenString: string, elseString: string,
+    offset: number): Result {
+  const condition = etm.getCondition(thenString).replace(' as ', '; as ');
+  const lbString = etm.hasLineBreaks ? '\n' : '';
+
+  const originals = getOriginals(etm, tmpl, offset);
+
+  const startBlock = `@if (${condition}) {${lbString}`;
+  const elseBlock = `${lbString}} @else {${lbString}`;
+
+  const thenPlaceholder = `#${etm.getTemplateName(thenString, elseString)}|`;
+  const elsePlaceholder = `#${etm.getTemplateName(elseString)}|`;
+
+  const postBlock = thenPlaceholder + elseBlock + elsePlaceholder + `${lbString}}`;
+  const ifThenElseBlock = startBlock + postBlock;
+
+  const tmplStart = tmpl.slice(0, etm.start(offset));
+  const tmplEnd = tmpl.slice(etm.end(offset));
+
+  const updatedTmpl = tmplStart + ifThenElseBlock + tmplEnd;
+
+  const pre = originals.start.length - startBlock.length;
+  const post = originals.end.length - postBlock.length;
+
+  return {tmpl: updatedTmpl, offsets: {pre, post}};
+}
diff --git a/packages/core/schematics/ng-generate/control-flow-migration/index.ts b/packages/core/schematics/ng-generate/control-flow-migration/index.ts
@@ -13,8 +13,11 @@ import {normalizePath} from '../../utils/change_tracker';
 import {getProjectTsConfigPaths} from '../../utils/project_tsconfig_paths';
 import {canMigrateFile, createMigrationProgram} from '../../utils/typescript/compiler_host';
 
+import {migrateFor} from './fors';
+import {migrateIf} from './ifs';
+import {migrateSwitch} from './switches';
 import {AnalyzedFile, MigrateError} from './types';
-import {analyze, migrateTemplate} from './util';
+import {analyze, processNgTemplates} from './util';
 
 interface Options {
   path: string;
@@ -84,7 +87,18 @@ function runControlFlowMigration(
     for (const [start, end] of ranges) {
       const template = content.slice(start, end);
       const length = (end ?? content.length) - start;
-      const {migrated, errors} = migrateTemplate(template);
+
+      const ifResult = migrateIf(template);
+      const forResult = migrateFor(ifResult.migrated);
+      const switchResult = migrateSwitch(forResult.migrated);
+
+      const errors = [
+        ...ifResult.errors,
+        ...forResult.errors,
+        ...switchResult.errors,
+      ];
+
+      const migrated = processNgTemplates(switchResult.migrated);
 
       if (migrated !== null) {
         update.remove(start, length);