chore: re-write @monocdk-experiment/rewrite-imports (#8401)

Improve the reliability of `@monocdk-experiment/rewrite-imports` by
making it use the TypeScript compiler to locate import statements that
need re-writing, and performing the relevant surgery on the source code
based on the findings.


----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@monocdk-experiment/rewrite-imports/bin/rewrite-imports.ts

@@ -3,10 +3,9 @@ import * as fs from 'fs';
 import * as _glob from 'glob';
 
 import { promisify } from 'util';
-import { rewriteFile } from '../lib/rewrite';
+import { rewriteImports } from '../lib/rewrite';
+
 const glob = promisify(_glob);
-const readFile = promisify(fs.readFile);
-const writeFile = promisify(fs.writeFile);
 
 async function main() {
   if (!process.argv[2]) {
@@ -21,10 +20,10 @@ async function main() {
 
   const files = await glob(process.argv[2], { ignore, matchBase: true });
   for (const file of files) {
-    const input = await readFile(file, 'utf-8');
-    const output = rewriteFile(input);
+    const input = await fs.promises.readFile(file, { encoding: 'utf8' });
+    const output = rewriteImports(input, file);
     if (output.trim() !== input.trim()) {
-      await writeFile(file, output);
+      await fs.promises.writeFile(file, output);
     }
   }
 }

packages/@monocdk-experiment/rewrite-imports/lib/rewrite.ts

@@ -1,24 +1,113 @@
-const exclude = [
-  '@aws-cdk/cloudformation-diff',
-  '@aws-cdk/assert',
-];
+import * as ts from 'typescript';
+
+/**
+ * Re-writes "hyper-modular" CDK imports (most packages in `@aws-cdk/*`) to the
+ * relevant "mono" CDK import path. The re-writing will only modify the imported
+ * library path, presrving the existing quote style, etc...
+ *
+ * Syntax errors in the source file being processed may cause some import
+ * statements to not be re-written.
+ *
+ * Supported import statement forms are:
+ * - `import * as lib from '@aws-cdk/lib';`
+ * - `import { Type } from '@aws-cdk/lib';`
+ * - `import '@aws-cdk/lib';`
+ * - `import lib = require('@aws-cdk/lib');`
+ * - `import { Type } = require('@aws-cdk/lib');
+ * - `require('@aws-cdk/lib');
+ *
+ * @param sourceText the source code where imports should be re-written.
+ * @param fileName   a customized file name to provide the TypeScript processor.
+ *
+ * @returns the updated source code.
+ */
+export function rewriteImports(sourceText: string, fileName: string = 'index.ts'): string {
+  const sourceFile = ts.createSourceFile(fileName, sourceText, ts.ScriptTarget.ES2018);
+
+  const replacements = new Array<{ original: ts.Node, updatedLocation: string }>();
+
+  const visitor = <T extends ts.Node>(node: T): ts.VisitResult<T> => {
+    const moduleSpecifier = getModuleSpecifier(node);
+    const newTarget = moduleSpecifier && updatedLocationOf(moduleSpecifier.text);
+
+    if (moduleSpecifier != null && newTarget != null) {
+      replacements.push({ original: moduleSpecifier, updatedLocation: newTarget });
+    }
 
-export function rewriteFile(source: string) {
-  const output = new Array<string>();
-  for (const line of source.split('\n')) {
-    output.push(rewriteLine(line));
+    return node;
+  };
+
+  sourceFile.statements.forEach(node => ts.visitNode(node, visitor));
+
+  let updatedSourceText = sourceText;
+  // Applying replacements in reverse order, so node positions remain valid.
+  for (const replacement of replacements.sort(({ original: l }, { original: r }) => r.getStart(sourceFile) - l.getStart(sourceFile))) {
+    const prefix = updatedSourceText.substring(0, replacement.original.getStart(sourceFile) + 1);
+    const suffix = updatedSourceText.substring(replacement.original.getEnd() - 1);
+
+    updatedSourceText = prefix + replacement.updatedLocation + suffix;
   }
-  return output.join('\n');
-}
 
-export function rewriteLine(line: string) {
-  for (const skip of exclude) {
-    if (line.includes(skip)) {
-      return line;
+  return updatedSourceText;
+
+  function getModuleSpecifier(node: ts.Node): ts.StringLiteral | undefined {
+    if (ts.isImportDeclaration(node)) {
+      // import style
+      const moduleSpecifier = node.moduleSpecifier;
+      if (ts.isStringLiteral(moduleSpecifier)) {
+        // import from 'location';
+        // import * as name from 'location';
+        return moduleSpecifier;
+      } else if (ts.isBinaryExpression(moduleSpecifier) && ts.isCallExpression(moduleSpecifier.right)) {
+        // import { Type } = require('location');
+        return getModuleSpecifier(moduleSpecifier.right);
+      }
+    } else if (
+      ts.isImportEqualsDeclaration(node)
+      && ts.isExternalModuleReference(node.moduleReference)
+      && ts.isStringLiteral(node.moduleReference.expression)
+    ) {
+      // import name = require('location');
+      return node.moduleReference.expression;
+    } else if (
+      (ts.isCallExpression(node))
+      && ts.isIdentifier(node.expression)
+      && node.expression.escapedText === 'require'
+      && node.arguments.length === 1
+    ) {
+      // require('location');
+      const argument = node.arguments[0];
+      if (ts.isStringLiteral(argument)) {
+        return argument;
+      }
+    } else if (ts.isExpressionStatement(node) && ts.isCallExpression(node.expression)) {
+      // require('location'); // This is an alternate AST version of it
+      return getModuleSpecifier(node.expression);
     }
+    return undefined;
   }
-  return line
-    .replace(/(["'])@aws-cdk\/assert(["'])/g, '$1@monocdk-experiment/assert$2') // @aws-cdk/assert  => @monocdk-experiment/assert
-    .replace(/(["'])@aws-cdk\/core(["'])/g, '$1monocdk-experiment$2')           // @aws-cdk/core    => monocdk-experiment
-    .replace(/(["'])@aws-cdk\/(.+)(["'])/g, '$1monocdk-experiment/$2$3');       // @aws-cdk/*       => monocdk-experiment/*;
+}
+
+const EXEMPTIONS = new Set([
+  '@aws-cdk/cloudformation-diff',
+]);
+
+function updatedLocationOf(modulePath: string): string | undefined {
+  if (!modulePath.startsWith('@aws-cdk/') || EXEMPTIONS.has(modulePath)) {
+    return undefined;
+  }
+
+  if (modulePath === '@aws-cdk/core') {
+    return 'monocdk-experiment';
+  }
+
+  if (modulePath === '@aws-cdk/assert') {
+    return '@monocdk-experiment/assert';
+  }
+
+  if (modulePath === '@aws-cdk/assert/jest') {
+    return '@monocdk-experiment/assert/jest';
+  }
+
+  return `monocdk-experiment/${modulePath.substring(9)}`;
 }

packages/@monocdk-experiment/rewrite-imports/package.json

@@ -31,7 +31,8 @@
   },
   "license": "Apache-2.0",
   "dependencies": {
-    "glob": "^7.1.6"
+    "glob": "^7.1.6",
+    "typescript": "~3.8.3"
   },
   "devDependencies": {
     "@types/glob": "^7.1.1",

packages/@monocdk-experiment/rewrite-imports/test/rewrite.test.ts

@@ -1,47 +1,75 @@
-import { rewriteFile, rewriteLine } from '../lib/rewrite';
+import { rewriteImports } from '../lib/rewrite';
 
-describe('rewriteLine', () => {
-  test('quotes', () => {
-    expect(rewriteLine('import * as s3 from \'@aws-cdk/aws-s3\''))
-      .toEqual('import * as s3 from \'monocdk-experiment/aws-s3\'');
-  });
+describe(rewriteImports, () => {
+  test('correctly rewrites naked "import"', () => {
+    const output = rewriteImports(`
+    // something before
+    import '@aws-cdk/assert/jest';
+    // something after
 
-  test('double quotes', () => {
-    expect(rewriteLine('import * as s3 from "@aws-cdk/aws-s3"'))
-      .toEqual('import * as s3 from "monocdk-experiment/aws-s3"');
-  });
+    console.log('Look! I did something!');`, 'subhect.ts');
+
+    expect(output).toBe(`
+    // something before
+    import '@monocdk-experiment/assert/jest';
+    // something after
 
-  test('@aws-cdk/core', () => {
-    expect(rewriteLine('import * as s3 from "@aws-cdk/core"'))
-      .toEqual('import * as s3 from "monocdk-experiment"');
-    expect(rewriteLine('import * as s3 from \'@aws-cdk/core\''))
-      .toEqual('import * as s3 from \'monocdk-experiment\'');
+    console.log('Look! I did something!');`);
   });
 
-  test('non-jsii modules are ignored', () => {
-    expect(rewriteLine('import * as cfndiff from \'@aws-cdk/cloudformation-diff\''))
-      .toEqual('import * as cfndiff from \'@aws-cdk/cloudformation-diff\'');
-    expect(rewriteLine('import * as cfndiff from \'@aws-cdk/assert'))
-      .toEqual('import * as cfndiff from \'@aws-cdk/assert');
+  test('correctly rewrites naked "require"', () => {
+    const output = rewriteImports(`
+    // something before
+    require('@aws-cdk/assert/jest');
+    // something after
+
+    console.log('Look! I did something!');`, 'subhect.ts');
+
+    expect(output).toBe(`
+    // something before
+    require('@monocdk-experiment/assert/jest');
+    // something after
+
+    console.log('Look! I did something!');`);
   });
-});
 
-describe('rewriteFile', () => {
-  const output = rewriteFile(`
+  test('correctly rewrites "import from"', () => {
+    const output = rewriteImports(`
   // something before
   import * as s3 from '@aws-cdk/aws-s3';
   import * as cfndiff from '@aws-cdk/cloudformation-diff';
-  import * as s3 from '@aws-cdk/core';
+  import { Construct } from "@aws-cdk/core";
   // something after
 
-  // hello`);
+  console.log('Look! I did something!');`, 'subject.ts');
 
-  expect(output).toEqual(`
+    expect(output).toBe(`
   // something before
   import * as s3 from 'monocdk-experiment/aws-s3';
   import * as cfndiff from '@aws-cdk/cloudformation-diff';
-  import * as s3 from 'monocdk-experiment';
+  import { Construct } from "monocdk-experiment";
+  // something after
+
+  console.log('Look! I did something!');`);
+  });
+
+  test('correctly rewrites "import = require"', () => {
+    const output = rewriteImports(`
+  // something before
+  import s3 = require('@aws-cdk/aws-s3');
+  import cfndiff = require('@aws-cdk/cloudformation-diff');
+  import { Construct } = require("@aws-cdk/core");
   // something after
 
-  // hello`);
-});
+  console.log('Look! I did something!');`, 'subject.ts');
+
+    expect(output).toBe(`
+  // something before
+  import s3 = require('monocdk-experiment/aws-s3');
+  import cfndiff = require('@aws-cdk/cloudformation-diff');
+  import { Construct } = require("monocdk-experiment");
+  // something after
+
+  console.log('Look! I did something!');`);
+  });
+});