Get working for eslint 8 with flowtype plugin (#33)

## Summary:
So, it was failing to resolve `eslint/use-at-your-own-risk` from inside a plugin.
I suspect this was down to module resoluton issues due to the way we programmatically require `eslint`.
So, rather than do that, I wrote it to invoke the CLI instead and let GitHub scrape the annotations (which it supports).

This feels more robust to future change by keeping the action's node module resolution independent of the code being checked.

I don't know why the lint step is doing what it's doing. I ran lint locally and all is fine - I suspect it may be suffering from the same issue that I'm fixing with this PR.

Issue: FEI-4138

## Test plan:
I added this to my webapp PR and checked that it now works (waiting on final confirmation, but it's doing far more than it was before these changes)
See https://github.com/Khan/webapp/runs/4292013711?check_suite_focus=true

Author: somewhatabstract

Reviewers: somewhatabstract, jeresig

Required Reviewers:

Approved By: jeresig

Checks: ❌ lint_and_unit, ✅ autofix

Pull Request URL: #33

.eslintrc

@@ -3,15 +3,20 @@
         "node": true,
         "jest": true
     },
-    "parser": "babel-eslint",
-    "parserOptions": {
-        "sourceType": "module"
-    },
-    "plugins": ["flowtype"],
+    "parser": "@babel/eslint-parser",
+    "plugins": [
+        "prettier",
+        "flowtype",
+        "@babel"
+    ],
     "rules": {
+        "prettier/prettier": "error",
         // The default rule wants to enforce // @flow, but we frequently have it
         // as part of the file's docstring.
-        "flowtype/require-valid-file-annotation": [0, "always"],
+        "flowtype/require-valid-file-annotation": [
+            0,
+            "always"
+        ],
         // ---------------------------------------
         // ES6 rules.
         "constructor-super": 2,
@@ -35,14 +40,25 @@
             2,
             {
                 "properties": "never",
-                "allow": ["^UNSAFE_"]
+                "allow": [
+                    "^UNSAFE_"
+                ]
             }
         ],
         "curly": 2,
-        "eqeqeq": [2, "allow-null"],
+        "eqeqeq": [
+            2,
+            "allow-null"
+        ],
         "guard-for-in": 2,
-        "linebreak-style": [2, "unix"],
-        "max-lines": [2, 1000],
+        "linebreak-style": [
+            2,
+            "unix"
+        ],
+        "max-lines": [
+            2,
+            1000
+        ],
         "no-alert": 2,
         "no-array-constructor": 2,
         "no-debugger": 2,
@@ -59,12 +75,24 @@
         // NOTE: If you change the options here, be sure to update eslintrc.flow also
         "no-unused-expressions": [
             2,
-            {"allowShortCircuit": true, "allowTernary": true}
+            {
+                "allowShortCircuit": true,
+                "allowTernary": true
+            }
+        ],
+        "no-unused-vars": [
+            2,
+            {
+                "args": "none",
+                "varsIgnorePattern": "^_*$"
+            }
         ],
-        "no-unused-vars": [2, {"args": "none", "varsIgnorePattern": "^_*$"}],
         "no-useless-call": 2,
         "no-with": 2,
-        "one-var": [2, "never"],
+        "one-var": [
+            2,
+            "never"
+        ],
         // TODO(scottgrant): Add additional a11y rules as we support them.
         // ---------------------------------------
         // Stuff that's disabled for now, but maybe shouldn't be.
@@ -76,16 +104,20 @@
         // use jsdoc anywhere it seems silly to require it yet.
         "valid-jsdoc": 0,
         "require-jsdoc": 0,
-        "flowtype/boolean-style": [2, "boolean"],
+        "flowtype/boolean-style": [
+            2,
+            "boolean"
+        ],
         "flowtype/define-flow-type": 1, // suppress no-undef on flow types
         "flowtype/no-dupe-keys": 2,
-
         // Use Flow's version of no-unused-expressions
         "flowtype/no-unused-expressions": [
             2,
-            {"allowShortCircuit": true, "allowTernary": true}
+            {
+                "allowShortCircuit": true,
+                "allowTernary": true
+            }
         ],
-
         "flowtype/no-weak-types": 0, // allow 'any' for now
         // flow may still require parameter types in certain situations
         "flowtype/require-parameter-type": 0,
@@ -94,11 +126,13 @@
         "flowtype/type-id-match": 0,
         "flowtype/use-flow-type": 1 // suppress no-unused-vars on flow types
     },
-    "extends": ["prettier/flowtype"],
+    "extends": [
+        "prettier"
+    ],
     "globals": {
-        "DEBUG": false,
-        "Promise": false,
-        "Set": false,
-        "__DEV__": [false /* writable */, true /* readable */]
+        "DEBUG": "readonly",
+        "Promise": "readonly",
+        "Set": "readonly",
+        "__DEV__": "readonly"
     }
-}
+}

.github/workflow-templates/pr-autofix.yml

@@ -25,7 +25,7 @@ jobs:
 
     - name: Run prettier
       setup: yarn
-      run: node ./node_modules/actions-utils/list-changed-files.js | grep '.*\.js$' | xargs npm run -s format-files
+      run: node ./node_modules/actions-utils/list-changed-files.js main | grep '.*\.js$' | xargs npm run -s format-files
 
     - name: Rebuild our "dist" file
       setup: yarn

.gitignore

@@ -2,3 +2,4 @@ node_modules
 .cache
 .idea
 coverage
+yarn-error.log

.prettierrc

@@ -1,4 +1,5 @@
 {
+    "parser": "babel-flow",
     "tabWidth": 4,
     "printWidth": 100,
     "trailingComma": "all",

__test__/empty.test.js

@@ -1,6 +1,5 @@
 // @flow
 
 describe('a test that does nothing', () => {
-    it('should work', async () => {
-    });
+    it('should work', async () => {});
 });