fix: use correct lint config for individual files (#167)

When invoked with a list of files, linter configuration pertaining to
those files should be preferred rather than the gts default config.

src/lint.ts

@@ -28,28 +28,54 @@ import {Options} from './cli';
  */
 export function lint(
     options: Options, files: string[] = [], fix = false): boolean {
-  const configPath =
-      fs.existsSync(path.join(options.targetRootDir, 'tslint.json')) ?
-      path.join(options.targetRootDir, 'tslint.json') :
-      path.join(options.gtsRootDir, 'tslint.json');
-
-  const program = createProgram(options);
-  const configuration = Configuration.findConfiguration(configPath, '').results;
-  const linter = new Linter({fix, formatter: 'codeFrame'}, program);
-  const srcFiles = files.length > 0 ? files : Linter.getFileNames(program);
-  srcFiles.forEach(file => {
-    const sourceFile = program.getSourceFile(file);
-    if (sourceFile) {
-      const fileContents = sourceFile.getFullText();
-      linter.lint(file, fileContents, configuration);
+  if (files.length > 0) {  // manually provided filenames.
+    const rcs = files.map(file => {
+      // Different config files may apply to each file.
+      const configPath = Configuration.findConfigurationPath(null, file) ||
+          path.join(options.gtsRootDir, 'tslint.json');
+
+      const configuration =
+          Configuration.loadConfigurationFromPath(configPath, '');
+      const source = fs.readFileSync(file, 'utf8');
+
+      const linter = new Linter({fix, formatter: 'codeFrame'});
+      linter.lint(file, source, configuration);
+      const result = linter.getResult();
+      if (result.errorCount || result.warningCount) {
+        options.logger.log(result.output);
+        return false;
+      }
+      return true;
+    });
+
+    return rcs.every(rc => rc);  // if all files succeeded.
+  } else {
+    // Lint the set of files specified by the typescript program config.
+    const program = createProgram(options);
+    files = Linter.getFileNames(program);
+
+    const configPath =
+        fs.existsSync(path.join(options.targetRootDir, 'tslint.json')) ?
+        path.resolve(options.targetRootDir, 'tslint.json') :
+        path.resolve(options.gtsRootDir, 'tslint.json');
+
+    const configuration = Configuration.loadConfigurationFromPath(configPath);
+    const linter = new Linter({fix, formatter: 'codeFrame'}, program);
+
+    files.forEach(file => {
+      const sourceFile = program.getSourceFile(file);
+      if (sourceFile) {
+        const fileContents = sourceFile.getFullText();
+        linter.lint(file, fileContents, configuration);
+      }
+    });
+    const result = linter.getResult();
+    if (result.errorCount || result.warningCount) {
+      options.logger.log(result.output);
+      return false;
     }
-  });
-  const result = linter.getResult();
-  if (result.errorCount || result.warningCount) {
-    options.logger.log(result.output);
-    return false;
+    return true;
   }
-  return true;
 }
 
 export function createProgram(options: Options): ts.Program {

test/test-lint.ts

@@ -135,20 +135,21 @@ test.serial('lint should lint only specified files', async t => {
       });
 });
 
-test.serial('lint should not throw for unrecognized files', async t => {
+test.serial('lint should throw for unrecognized files', async t => {
   await withFixtures(
       {
         'tsconfig.json': JSON.stringify({}),
         'a.ts': GOOD_CODE,
       },
       async () => {
-        lint.lint(OPTIONS, ['z.ts']);
-        t.pass();
+        t.throws(() => {
+          lint.lint(OPTIONS, ['z.ts']);
+        });
       });
 });
 
 test.serial('lint should prefer user config file over default', async t => {
-  const CUSTOM_LINT_CODE = 'const t: Object;';
+  const CUSTOM_LINT_CODE = 'debugger;';
 
   // By defualt the above should fail lint.
   await withFixtures(
@@ -158,7 +159,7 @@ test.serial('lint should prefer user config file over default', async t => {
       },
       async () => {
         const okay = lint.lint(OPTIONS);
-        t.is(okay, false);
+        t.false(okay);
       });
 
   // User should be able to override the default config.
@@ -170,8 +171,40 @@ test.serial('lint should prefer user config file over default', async t => {
       },
       async () => {
         const okay = lint.lint(OPTIONS);
-        t.is(okay, true);
+        t.true(okay);
       });
 });
 
+test.serial(
+    'lint for specific files should use file-specific config', async t => {
+      const CODE_WITH_PARSEINT = 'parseInt(42);';
+      let logBuffer = '';
+      const optionsWithLog = Object.assign({}, OPTIONS, {
+        logger: {
+          log: (...args: string[]) => {
+            logBuffer += (args.join(' '));
+          },
+          error: nop,
+          dir: nop
+        }
+      });
+      await withFixtures(
+          {
+            dira: {
+              'a.ts': CODE_WITH_PARSEINT,
+              // no tslint, so default should apply.
+            },
+            dirb: {
+              'b.ts': CODE_WITH_PARSEINT,
+              'tslint.json': JSON.stringify({})
+            }
+          },
+          async () => {
+            const okay = lint.lint(optionsWithLog, ['dira/a.ts', 'dirb/b.ts']);
+            t.false(okay);
+            t.regex(logBuffer, /dira\/a\.ts/);
+            t.notRegex(logBuffer, /dirb\/b\.ts/);
+          });
+    });
+
 // TODO: test for when tsconfig.json is missing.