chore: Rewrite lint:imports & add component dep check

This PR refactors `npm run lint:imports` and adds a new check for component-dependent imports in non-component files.

Example error messages:

```
ERROR: mdc-textfield/foundation.ts: Import path '@material/base/index'
is only allowed in component.ts and index.ts files. Please import a more specific file
(e.g., 'adapter', 'foundation', 'types').
This keeps byte sizes smaller for wrapper libraries that only use our foundations.

ERROR: mdc-textfield/component.ts: Import path '@material/base'
should point directly to a specific TypeScript file.
E.g.: import '@material/base/index'

ERROR: mdc-textfield/index.ts: Import path './character-counter'
should point directly to a specific TypeScript file.
E.g.: import './character-counter/index'

ERROR: mdc-textfield/component.ts: Import path '@material/dom/ponyfill'
references NPM module '@material/dom', but that module
is not listed in package.json dependencies.

ERROR: mdc-textfield/index.ts: Import path '../mdc-textfield/helper-text/index'
appears to be a relative path to an MDC package. Please use a @Material import instead.
E.g.: import '@material/foo/types' instead of import '../mdc-foo/types'.

ERROR: mdc-textfield/foundation.ts: Import path
'/Users/advorak/dev/mdc-web/packages/mdc-textfield/adapter'
appears to be an absolute path. Please use a relative path instead.
```

![screenshot](https://user-images.githubusercontent.com/409245/53447057-31e7df00-39c9-11e9-9a80-1d3e97763a09.png)

package.json

@@ -20,7 +20,7 @@
     "lint:js": "eslint test scripts webpack.config.js demos/webpack.config.js karma.conf.js",
     "lint:ts": "tslint --exclude \"**/*.d.ts\" \"packages/**/*.ts\" \"test/**/*.ts\" \"scripts/**/*.ts\"",
     "lint:html": "find test/screenshot/spec/ -name '*.html' | grep -v 'index.html$' | xargs htmllint",
-    "lint:imports": "node scripts/check-imports.js",
+    "lint:imports": "node scripts/lint-imports.js",
     "lint": "npm-run-all --parallel lint:*",
     "postinstall": "lerna bootstrap",
     "pretest": "npm run lint",

scripts/lint-imports.js

@@ -0,0 +1,190 @@
+/**
+ * @license
+ * Copyright 2019 Google Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * @fileoverview Custom linter for TypeScript imports.
+ */
+
+const fs = require('fs');
+const glob = require('glob');
+const parser = require('@babel/parser');
+const path = require('path');
+const recast = require('recast');
+const resolve = require('resolve');
+const colors = require('colors/safe');
+const {default: traverse} = require('babel-traverse');
+
+let violationCount = 0;
+
+const packagesDir = path.resolve(__dirname, '../packages');
+
+lintAllFiles();
+
+function lintAllFiles() {
+  const searchPattern = path.join(packagesDir, '**/*.ts');
+  const inputFilePaths = glob.sync(searchPattern, {
+    nodir: true,
+    ignore: ['**/node_modules/**', '**/dist/**', '**/*.d.ts'],
+  });
+
+  const customLinterAnsi = colors.bold.yellow('Import Linter');
+  console.log(`${customLinterAnsi}: Checking ${inputFilePaths.length.toLocaleString()} TypeScript files...\n`);
+
+  for (const inputFilePath of inputFilePaths) {
+    const inputCode = fs.readFileSync(inputFilePath, 'utf8');
+    lintOneFile(inputFilePath, inputCode);
+  }
+
+  const violationCountAnsi = colors.bold(violationCount);
+  const plural = violationCount === 1 ? '' : 's';
+  console.log(`\n${violationCountAnsi} Import Linter error${plural}\n`);
+}
+
+/**
+ * @param {string} inputFilePath
+ * @param {string} inputCode
+ */
+function lintOneFile(inputFilePath, inputCode) {
+  checkAllImportPaths(inputFilePath, inputCode);
+}
+
+/**
+ * @param {string} inputFilePath
+ * @param {string} inputCode
+ */
+function checkAllImportPaths(inputFilePath, inputCode) {
+  const ast = getAstFromCodeString(inputCode);
+
+  traverse(ast, {
+    ExportDeclaration(oldExportDeclaration) {
+      checkOneImportPath(oldExportDeclaration, inputFilePath);
+    },
+    ImportDeclaration(oldImportDeclaration) {
+      checkOneImportPath(oldImportDeclaration, inputFilePath);
+    },
+  });
+}
+
+/**
+ * @param {!Object} importOrExportDeclaration
+ * @param {string} inputFilePath
+ */
+function checkOneImportPath(importOrExportDeclaration, inputFilePath) {
+  // Ensure exports have a `from '...'` qualifier.
+  if (!importOrExportDeclaration.node.source) {
+    return;
+  }
+
+  const inputFileDir = path.dirname(inputFilePath);
+
+  /** @type {string} */
+  const importPath = importOrExportDeclaration.node.source.value;
+  const importPathAnsi = colors.bold(importPath);
+
+  /** @type {string} */
+  const resolvedAbsolutePathWithExt = resolve.sync(importPath, {basedir: inputFileDir, extensions: ['.ts', '.js']});
+  const resolvedFileNameWithoutExt = path.parse(resolvedAbsolutePathWithExt).name;
+
+  const isLocalFileImport = resolvedAbsolutePathWithExt.indexOf('node_modules') === -1;
+  const isMaterialNpmImport = importPath.startsWith('@material/');
+  const isThirdPartyImport = !isMaterialNpmImport && !isLocalFileImport;
+
+  // Make sure npm modules are specified in package.json dependencies
+  if (isMaterialNpmImport || isThirdPartyImport) {
+    const inputFilePackageDir = inputFilePath.replace(new RegExp('(packages/[^/]+)/.+'), '$1');
+    const inputFilePackageJson = require(path.join(inputFilePackageDir, 'package.json'));
+    const expectedNpmDep = importPath
+      // "@material/foo/bar" -> "@material/foo"
+      .replace(new RegExp('^(@[^/]+/[^/]+)/.+'), '$1')
+      // "focus-trap/foo" -> "focus-trap"
+      .replace(new RegExp('^([^@][^/]+)/.+'), '$1')
+    ;
+    /** @type {!Object<string, string>|undefined} */
+    const inputFilePackageJsonDeps = inputFilePackageJson.dependencies;
+    if (!inputFilePackageJsonDeps || !inputFilePackageJsonDeps[expectedNpmDep]) {
+      logLinterViolation(
+        inputFilePath,
+        // eslint-disable-next-line max-len
+        `Import path '${importPathAnsi}' references NPM module '${expectedNpmDep}', but that module is not listed in package.json dependencies.`
+      );
+    }
+  }
+
+  if (!isThirdPartyImport && !importPath.endsWith(`/${resolvedFileNameWithoutExt}`)) {
+    logLinterViolation(
+      inputFilePath,
+      // eslint-disable-next-line max-len
+      `Import path '${importPathAnsi}' should point directly to a specific TypeScript file. E.g.: import '${importPath}/index'`
+    );
+  }
+
+  if (path.isAbsolute(importPath)) {
+    logLinterViolation(
+      inputFilePath,
+      // eslint-disable-next-line max-len
+      `Import path '${importPathAnsi}' appears to be an absolute path. Please use a relative path instead.`
+    );
+  }
+
+  if (importPath.indexOf('../mdc-') > -1 || importPath.indexOf('../material-components-web') > -1) {
+    logLinterViolation(
+      inputFilePath,
+      // eslint-disable-next-line max-len
+      `Import path '${importPathAnsi}' appears to be a relative path to an MDC package. Please use a @material import instead. E.g.: import '@material/foo/types' instead of import '../mdc-foo/types'.`
+    );
+  }
+
+  const importPathIsComponent = importPath.endsWith('/index') || importPath.endsWith('/component');
+  const inputFileIsComponent = inputFilePath.endsWith('/index.ts') || inputFilePath.endsWith('/component.ts');
+  if (importPathIsComponent && !inputFileIsComponent) {
+    logLinterViolation(
+      inputFilePath,
+      // eslint-disable-next-line max-len
+      `Import path '${importPathAnsi}' is only allowed in component.ts and index.ts files. Please import a more specific file (e.g., 'adapter', 'foundation', 'types'). This keeps byte sizes smaller for wrapper libraries that only use our foundations.`
+    );
+  }
+}
+
+// TODO(acdvorak): Add `npm run fix:imports` mode to automatically rewrite the AST when possible?
+function logLinterViolation(inputFilePath, message) {
+  const errorAnsi = colors.red('ERROR');
+  const inputFilePathAnsi = colors.bold(path.relative(packagesDir, inputFilePath));
+  console.error(`${errorAnsi}: ${inputFilePathAnsi}: ${message}`);
+  process.exitCode = 1;
+  violationCount++;
+}
+
+/**
+ * @param {string} inputCode
+ * @return {!Object} AST for inputCode
+ */
+function getAstFromCodeString(inputCode) {
+  return recast.parse(inputCode, {
+    parser: {
+      parse: (code) => parser.parse(code, {
+        sourceType: 'module',
+        plugins: ['typescript', 'classProperties'],
+      }),
+    },
+  });
+}