fix: fix with --dry-run should not modify files

src/lint.ts

@@ -24,10 +24,16 @@ import {Options} from './cli';
  * Run tslint with the default configuration. Returns true on success.
  * @param options gts options
  * @param files files to run linter on
- * @param fix automatically fix linter errors
+ * @param fix automatically fix linter errors. Ignored when options.dryRun is
+ *            set.
  */
 export function lint(
     options: Options, files: string[] = [], fix = false): boolean {
+  if (options.dryRun && fix) {
+    options.logger.log('lint: skipping auto fix since --dry-run was passed');
+    fix = false;
+  }
+
   if (files.length > 0) {  // manually provided filenames.
     const rcs = files.map(file => {
       // Different config files may apply to each file.

test/test-lint.ts

@@ -15,6 +15,7 @@
  */
 
 import test from 'ava';
+import fs from 'fs';
 import * as path from 'path';
 
 import {Options} from '../src/cli';
@@ -35,6 +36,10 @@ const OPTIONS: Options = {
 const BAD_CODE = `throw 'hello world';`;
 const GOOD_CODE = `throw new Error('hello world');`;
 
+// missing semicolon, array-type simple.
+const FIXABLE_CODE = 'const x : Array<string> = []';
+const FIXABLE_CODE_FIXED = 'const x : string[] = [];';
+
 test.serial('createProgram should return an object', async t => {
   await withFixtures({'tsconfig.json': '{}'}, async () => {
     const program = lint.createProgram(OPTIONS);
@@ -66,6 +71,37 @@ test.serial('lint should return false on bad code', async t => {
       });
 });
 
+test.serial('lint should auto fix fixable errors', async t => {
+  await withFixtures(
+      {
+        'tsconfig.json': JSON.stringify({files: ['a.ts']}),
+        'a.ts': FIXABLE_CODE
+      },
+      async (fixturesDir) => {
+        const okay = lint.lint(OPTIONS, [], true);
+        t.is(okay, true);
+        const contents =
+            fs.readFileSync(path.join(fixturesDir, 'a.ts'), 'utf8');
+        t.deepEqual(contents, FIXABLE_CODE_FIXED);
+      });
+});
+
+test.serial('lint should not auto fix on dry-run', async t => {
+  await withFixtures(
+      {
+        'tsconfig.json': JSON.stringify({files: ['a.ts']}),
+        'a.ts': FIXABLE_CODE
+      },
+      async (fixturesDir) => {
+        const optionsWithDryRun = Object.assign({}, OPTIONS, {dryRun: true});
+        const okay = lint.lint(optionsWithDryRun, [], true);
+        t.is(okay, false);
+        const contents =
+            fs.readFileSync(path.join(fixturesDir, 'a.ts'), 'utf8');
+        t.deepEqual(contents, FIXABLE_CODE);
+      });
+});
+
 test.serial('lint should lint files listed in tsconfig.files', async t => {
   await withFixtures(
       {
@@ -94,6 +130,25 @@ test.serial(
           });
     });
 
+test.serial(
+    'lint should lint files listed in tsconfig.files when empty list is provided',
+    async t => {
+      await withFixtures(
+          {
+            'tsconfig.json': JSON.stringify({files: ['a.ts']}),
+            'a.ts': FIXABLE_CODE,
+            'b.ts': BAD_CODE
+          },
+          async (fixturesDir) => {
+            const okay = lint.lint(OPTIONS, [], true);
+            t.is(okay, true);
+            const contents =
+                fs.readFileSync(path.join(fixturesDir, 'a.ts'), 'utf8');
+            t.deepEqual(contents, FIXABLE_CODE_FIXED);
+          });
+    });
+
+
 test.serial('lint should not lint files listed in exclude', async t => {
   await withFixtures(
       {