add/configure eslint

.github/workflows/build.yml

@@ -29,6 +29,9 @@ jobs:
       - name: test if all files have been formatted with prettier
         run: npx prettier -c src/**/*.ts
 
+      - name: linting/static code analysis
+        run: npx eslint src
+
       - name: run tests
         run: npx jest
 

Justfile

@@ -8,6 +8,7 @@ ci:
     npm ci
     npm run tsc
     npm run prettier
+    npm run eslint
     # currently no tests…
     npm run test
 

eslint.config.js

@@ -0,0 +1,45 @@
+const eslint = require("@eslint/js");
+const tseslint = require("typescript-eslint");
+const eslintConfigPrettier = require("eslint-config-prettier");
+
+module.exports = tseslint.config(
+  {
+    ignores: ["eslint.config.js"],
+  },
+  eslint.configs.recommended,
+  eslintConfigPrettier,
+  ...tseslint.configs.recommendedTypeChecked,
+  {
+    languageOptions: {
+      parserOptions: {
+        project: true,
+        tsconfigRootDir: __dirname,
+      },
+    },
+    rules: {
+      // emulate TS behaviour (if noUnusedLocals and noUnusedParameters are enabled): https://typescript-eslint.io/rules/no-unused-vars/#benefits-over-typescript
+      "@typescript-eslint/no-unused-vars": [
+        "error",
+        {
+          args: "all",
+          argsIgnorePattern: "^_",
+          caughtErrors: "all",
+          caughtErrorsIgnorePattern: "^_",
+          destructuredArrayIgnorePattern: "^_",
+          varsIgnorePattern: "^_",
+          ignoreRestSiblings: true,
+        },
+      ],
+      // to use promises in express (and catch rejecting promises!) we use express-promise-router, it allows promises,
+      // but does not define the type correctly: https://github.com/express-promise-router/express-promise-router/issues/230
+      "@typescript-eslint/no-misused-promises": [
+        "error",
+        {
+          checksVoidReturn: {
+            arguments: false,
+          },
+        },
+      ],
+    },
+  },
+);