Setup eslint

Enabled default rules plus `require-await` to catch any promises that
are left un-awaited.

eslint.config.js

@@ -0,0 +1,14 @@
+import globals from 'globals';
+import pluginJs from '@eslint/js';
+import tseslint from 'typescript-eslint';
+
+/** @type {import('eslint').Linter.FlatConfig[]} */
+const config = [
+    { files: ['src/**/*.ts'], ignores: ['build/**/*'] },
+    { languageOptions: { globals: globals.node } },
+    { rules: { 'require-await': 'error' } },
+    pluginJs.configs.recommended,
+    ...tseslint.configs.recommended,
+];
+
+export default config;

package.json

@@ -36,15 +36,17 @@
     },
     "scripts": {
         "clean": "rimraf './build'",
+        "lint": "cross-env ./node_modules/.bin/eslint src scripts",
         "build": "npm run clean && node ./scripts/build.mjs",
         "build:dev": "npm run build -- --watch",
         "build:publish": "npm run build -- --prod",
         "test": "cross-env ./node_modules/.bin/tsc && cross-env NODE_OPTIONS=\"--experimental-vm-modules --no-warnings\" ./node_modules/.bin/jest",
         "previewTheme": "nodemon -q build/previewTheme.mjs",
         "benchmark": "npm run build && node build/benchmark.mjs",
-        "prepublishOnly": "npm run build:publish && npm run test"
+        "prepublishOnly": "npm run lint && npm run build:publish && npm run test"
     },
     "devDependencies": {
+        "@eslint/js": "^9.6.0",
         "@types/benchmark": "^2.1.0",
         "@types/diff": "^5.0.0",
         "@types/jest": "^29.5.1",
@@ -53,12 +55,15 @@
         "benchmark": "^2.1.4",
         "cross-env": "^7.0.3",
         "esbuild": "^0.17.18",
+        "eslint": "^9.6.0",
+        "globals": "^15.8.0",
         "jest": "^29.7.0",
         "nodemon": "^2.0.7",
         "prettier": "^2.2.1",
         "rimraf": "^5.0.5",
         "ts-jest": "^29.1.0",
-        "typescript": "^5.0.4"
+        "typescript": "^5.0.4",
+        "typescript-eslint": "^7.15.0"
     },
     "packageManager": "npm@9.8.1"
 }

src/getGitConfig.ts

@@ -11,7 +11,7 @@ export const DEFAULT_THEME_NAME = 'dark';
 
 const GIT_CONFIG_KEY_PREFIX = 'split-diffs';
 const GIT_CONFIG_LINE_REGEX = new RegExp(
-    `${GIT_CONFIG_KEY_PREFIX}\.([^=]+)=(.*)`
+    `${GIT_CONFIG_KEY_PREFIX}\\.([^=]+)=(.*)`
 );
 
 function extractFromGitConfigString(configString: string) {
@@ -36,7 +36,9 @@ export function getGitConfig(configString: string): GitConfig {
         if (!isNaN(parsedMinLineWidth)) {
             minLineWidth = parsedMinLineWidth;
         }
-    } catch {}
+    } catch {
+        // Ignore invalid values
+    }
 
     return {
         MIN_LINE_WIDTH: minLineWidth,

src/index.test.ts

@@ -10,6 +10,7 @@ const TEST_THEME = Object.fromEntries(
 ) as Theme;
 
 const replaceColoredText =
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
     (r: number, g: number, b: number) => (text: string) =>
         text.replace(/./g, '░');
 
@@ -164,7 +165,7 @@ index 9f14e96..eaf3730 100644
             ).toMatchSnapshot();
         });
 
-        test('commit with deletion', async function () {
+        test('commit with deletion', function () {
             expect(`commit eccfb5a2b3d76ba53df315f977da74b18d50113e
 Author: Shrey Banga <shrey@quip.com>
 Date:   Thu Aug 22 10:07:25 2019 -0700
@@ -316,7 +317,7 @@ index 0000000..6499edf
 @@ -0,0 +1,2 @@
 +node_modules/**
 +build/**
-\ No newline at end of file`)
+\\ No newline at end of file`)
             ).toMatchSnapshot();
         });
 
@@ -380,7 +381,7 @@ index ca15c64..0000000
 -        end tell
 -    end timeout
 -end run
-\ No newline at end of file`)
+\\ No newline at end of file`)
             ).toMatchSnapshot();
         });
 
@@ -465,7 +466,7 @@ index d88c464..6901818 100644
 +++ b/file1
 @@ -1 +1,2 @@
 -This is file1
-\ No newline at end of file
+\\ No newline at end of file
 +This is file1
 +Experimental change
 diff --git a/file2 b/file2

src/iterFormatHunkUnified.ts

@@ -14,10 +14,11 @@ export async function* iterFormatUnifiedDiffHunkUnified(
 ): AsyncIterable<FormattedString> {
     const lineWidth = context.SCREEN_WIDTH;
 
-    let [
-        { fileName: fileNameA, lines: hunkLinesA, startLineNo: lineNoA },
-        { fileName: fileNameB, lines: hunkLinesB, startLineNo: lineNoB },
+    const [
+        { fileName: fileNameA, lines: hunkLinesA },
+        { fileName: fileNameB, lines: hunkLinesB },
     ] = hunkParts;
+    let [{ startLineNo: lineNoA }, { startLineNo: lineNoB }] = hunkParts;
 
     let indexA = 0,
         indexB = 0;
@@ -108,7 +109,7 @@ export async function* iterFormatCombinedDiffHunkUnified(
 
     // The final hunk part shows the current state of the file, so we just
     // display that with additions and deletions highlighted.
-    let { fileName, lines, startLineNo } = hunkParts[hunkParts.length - 1];
+    const { fileName, lines, startLineNo } = hunkParts[hunkParts.length - 1];
     let lineNo = startLineNo;
     let numDeletes = 0;
 

src/themes.ts

@@ -82,7 +82,7 @@ function hexToRgba(hex: string): ColorRgba {
     hex = hex.slice(1);
 
     let hexNo = parseInt(hex, 16);
-    let bits = hex.length === 3 ? 4 : 8;
+    const bits = hex.length === 3 ? 4 : 8;
 
     let a = 255;
     if (hex.length === 8) {

src/transformContentsStreaming.ts

@@ -5,7 +5,7 @@ import { iterReplaceTabsWithSpaces } from './iterReplaceTabsWithSpaces';
 import { iterSideBySideDiffs } from './iterSideBySideDiffs';
 import { iterWithNewlines } from './iterWithNewlines';
 
-export async function transformContentsStreaming(
+export function transformContentsStreaming(
     context: Context,
     input: Readable,
     output: Writable

src/zip.ts

@@ -1,4 +1,4 @@
-export function* zip<T extends Array<any>>(
+export function* zip<T extends Array<unknown>>(
     ...iterables: { [K in keyof T]: Iterable<T[K]> }
 ): Iterable<{ [K in keyof T]: T[K] | undefined }> {
     const iterators = iterables.map((iterable) => iterable[Symbol.iterator]());
@@ -18,7 +18,7 @@ export function* zip<T extends Array<any>>(
     }
 }
 
-export async function* zipAsync<T extends Array<any>>(
+export async function* zipAsync<T extends Array<unknown>>(
     ...iterables: { [K in keyof T]: AsyncIterable<T[K]> }
 ): AsyncIterable<{ [K in keyof T]: T[K] | undefined }> {
     const iterators = iterables.map((iterable) =>

todo.md

@@ -41,4 +41,4 @@
 -   [ ] Support custom themes
 -   [x] Calculate correct display widths, e.g. https://github.com/microsoft/MS-DOS/commit/29a0f9c130b6883080046b830e27403a289de72d
 -   [ ] Add a theme without background colors
--   [ ] Add eslint rule to check for async/await gotchas
+-   [x] Add eslint rule to check for async/await gotchas