feat: Support ESLint fix option

Closes: #323

Author: Methuselah96

README.md

@@ -114,7 +114,7 @@ There's a good explanation on setting up TypeScript ESLint support by Robert Coo
 
 - **eslintOptions** `object`:
 
-  - Options that can be used to initialise ESLint. See https://eslint.org/docs/1.0.0/developer-guide/nodejs-api#cliengine
+  - Options that can be used to initialise ESLint. See https://eslint.org/docs/developer-guide/nodejs-api#cliengine
 
 - **async** `boolean`:
   True by default - `async: false` can block webpack's emit to wait for type checker/linter and to add errors to the webpack's compilation.

src/createEslinter.ts

@@ -1,13 +1,13 @@
 import * as path from 'path';
 
-import { LintReport } from './types/eslint';
+import { LintReport, Options as EslintOptions } from './types/eslint';
 import { throwIfIsInvalidSourceFileError } from './FsHelper';
 
-export function createEslinter(eslintOptions: object) {
+export function createEslinter(eslintOptions: EslintOptions) {
   // eslint-disable-next-line @typescript-eslint/no-var-requires
   const { CLIEngine } = require('eslint');
 
-  // See https://eslint.org/docs/1.0.0/developer-guide/nodejs-api#cliengine
+  // See https://eslint.org/docs/developer-guide/nodejs-api#cliengine
   const eslinter = new CLIEngine(eslintOptions);
 
   function getReport(filepath: string): LintReport | undefined {
@@ -21,7 +21,13 @@ export function createEslinter(eslintOptions: object) {
         return undefined;
       }
 
-      return eslinter.executeOnFiles([filepath]);
+      const lintReport = eslinter.executeOnFiles([filepath]);
+
+      if (eslintOptions && eslintOptions.fix) {
+        eslinter.outputFixes(lintReport);
+      }
+
+      return lintReport;
     } catch (e) {
       throwIfIsInvalidSourceFileError(filepath, e);
     }

src/index.ts

@@ -21,6 +21,7 @@ import { getForkTsCheckerWebpackPluginHooks } from './hooks';
 import { RUN, RunPayload, RunResult } from './RpcTypes';
 import { Issue, IssueSeverity } from './issue';
 import { VueOptions } from './types/vue-options';
+import { Options as EslintOptions } from './types/eslint';
 
 const checkerPluginName = 'fork-ts-checker-webpack-plugin';
 
@@ -39,8 +40,8 @@ namespace ForkTsCheckerWebpackPlugin {
     tsconfig: string;
     compilerOptions: object;
     eslint: boolean;
-    /** Options to supply to eslint https://eslint.org/docs/1.0.0/developer-guide/nodejs-api#cliengine */
-    eslintOptions: object;
+    /** Options to supply to eslint https://eslint.org/docs/developer-guide/nodejs-api#cliengine */
+    eslintOptions: EslintOptions;
     async: boolean;
     ignoreDiagnostics: number[];
     ignoreLints: string[];
@@ -79,7 +80,7 @@ class ForkTsCheckerWebpackPlugin {
   private tsconfig: string;
   private compilerOptions: object;
   private eslint = false;
-  private eslintOptions: object = {};
+  private eslintOptions: EslintOptions = {};
   private ignoreDiagnostics: number[];
   private ignoreLints: string[];
   private ignoreLintWarnings: boolean;

src/types/eslint.ts

@@ -34,3 +34,13 @@ export interface LintReport {
   fixableErrorCount: number;
   fixableWarningCount: number;
 }
+
+export interface Options {
+  fix?: boolean;
+
+  // The rest of the properties are not specified here because they are not
+  // directly used by this package and are instead just passed to eslint.
+  // We do this in order to avoid a dependency on @types/eslint (since the use
+  // of eslint is optional) and to avoid copying types from @types/eslint.
+  [key: string]: any;
+}