build: ensure that there are no invalid dynamic imports (#14619)

**Note**: In a follow-up I want to wire up the release output validations as part of a CircleCI job. It just makes sense to keep all of these release output validations in the same place.

References https://github.com/angular/material2/issues/12877

tools/release/release-output/check-packages.ts

@@ -2,11 +2,18 @@ import {bold, red, yellow} from 'chalk';
 import {existsSync} from 'fs';
 import {sync as glob} from 'glob';
 import {join} from 'path';
-import {checkMaterialPackage, checkReleaseBundle} from './output-validations';
+import {
+  checkMaterialPackage,
+  checkReleaseBundle,
+  checkTypeDefinitionFile
+} from './output-validations';
 
 /** Glob that matches all JavaScript bundle files within a release package. */
 const releaseBundlesGlob = '+(esm5|esm2015|bundles)/*.js';
 
+/** Glob that matches all TypeScript definition files within a release package. */
+const releaseTypeDefinitionsGlob = '**/*.d.ts';
+
 /**
  * Type that describes a map of package failures. The keys are failure messages and
  * their value is an array of specifically affected files.
@@ -21,12 +28,14 @@ type PackageFailures = Map<string, string[]>;
  */
 export function checkReleasePackage(releasesPath: string, packageName: string): boolean {
   const packagePath = join(releasesPath, packageName);
-  const bundlePaths = glob(releaseBundlesGlob, {cwd: packagePath, absolute: true});
   const failures = new Map() as PackageFailures;
   const addFailure = (message, filePath?) => {
     failures.set(message, (failures.get(message) || []).concat(filePath));
   };
 
+  const bundlePaths = glob(releaseBundlesGlob, {cwd: packagePath, absolute: true});
+  const typeDefinitions = glob(releaseTypeDefinitionsGlob, {cwd: packagePath, absolute: true});
+
   // We want to walk through each bundle within the current package and run
   // release validations that ensure that the bundles are not invalid.
   bundlePaths.forEach(bundlePath => {
@@ -34,6 +43,12 @@ export function checkReleasePackage(releasesPath: string, packageName: string):
       .forEach(message => addFailure(message, bundlePath));
   });
 
+  // Run output validations for all TypeScript definition files within the release output.
+  typeDefinitions.forEach(filePath => {
+    checkTypeDefinitionFile(filePath)
+      .forEach(message => addFailure(message, filePath));
+  });
+
   // Special release validation checks for the "material" release package.
   if (packageName === 'material') {
     checkMaterialPackage(join(releasesPath, packageName))

tools/release/release-output/output-validations.ts

@@ -1,6 +1,7 @@
 import {existsSync, readFileSync} from 'fs';
 import {sync as glob} from 'glob';
-import {join} from 'path';
+import {dirname, isAbsolute, join} from 'path';
+import * as ts from 'typescript';
 
 /** RegExp that matches Angular component inline styles that contain a sourcemap reference. */
 const inlineStylesSourcemapRegex = /styles: ?\[["'].*sourceMappingURL=.*["']/;
@@ -14,7 +15,7 @@ const externalReferencesRegex = /(templateUrl|styleUrls): *["'[]/;
  */
 export function checkReleaseBundle(bundlePath: string): string[] {
   const bundleContent = readFileSync(bundlePath, 'utf8');
-  let failures: string[] = [];
+  const failures: string[] = [];
 
   if (inlineStylesSourcemapRegex.exec(bundleContent) !== null) {
     failures.push('Found sourcemap references in component styles.');
@@ -27,6 +28,46 @@ export function checkReleaseBundle(bundlePath: string): string[] {
   return failures;
 }
 
+/**
+ * Checks the specified TypeScript definition file by ensuring it does not contain invalid
+ * dynamic import statements. There can be invalid type imports paths because we compose the
+ * release package by moving things in a desired output structure. See Angular package format
+ * specification and https://github.com/angular/material2/pull/12876
+ */
+export function checkTypeDefinitionFile(filePath: string): string[] {
+  const baseDir = dirname(filePath);
+  const fileContent = readFileSync(filePath, 'utf8');
+  const failures = [];
+
+  const sourceFile = ts.createSourceFile(filePath, fileContent, ts.ScriptTarget.Latest, true);
+  const nodeQueue = [...sourceFile.getChildren()];
+
+  while (nodeQueue.length) {
+    const node = nodeQueue.shift()!;
+
+    // Check all dynamic type imports and ensure that the import path is valid within the release
+    // output. Note that we don't want to enforce that there are no dynamic type imports because
+    // type inference is heavily used within the schematics and is useful in some situations.
+    if (ts.isImportTypeNode(node) && ts.isLiteralTypeNode(node.argument) &&
+        ts.isStringLiteral(node.argument.literal)) {
+      const importPath = node.argument.literal.text;
+
+      // In case the type import path starts with a dot, we know that this is a relative path
+      // and can ensure that the target path exists. Note that we cannot completely rely on
+      // "isAbsolute" because dynamic imports can also import from modules (e.g. "my-npm-module")
+      if (importPath.startsWith('.') && !existsSync(join(baseDir, `${importPath}.d.ts`))) {
+        failures.push('Found relative type imports which do not exist.');
+      } else if (isAbsolute(importPath)) {
+        failures.push('Found absolute type imports in definition file.');
+      }
+    }
+
+    nodeQueue.push(...node.getChildren());
+  }
+
+  return failures;
+}
+
 /**
  * Checks the Angular Material release package and ensures that prebuilt themes
  * and the theming bundle are built properly.