Add support for alternative config files with cosmiconfig (#178)

Fixes #118 

Introduces `cosmiconfig` as requested in #118 in order to support
loading the config from alternative file formats like:
```
.unimportedrc.js
.unimportedrc.yml
package.json > "unimported" key
```

I'm using `cosmiconfigSync` utilities instead of the async version,
despite them being available since the `getConfig` is an async method.
When we use the async equivalent, we hit a segfault in Node as a result
of `cosmiconfig` trying to call a dynamic import on the file within a
Jest context that doesn't allow it to. Patched in a recent version of
Node, and once the test infra can require the latest version it should
be fine to switch to the async version.

See nodejs/node#35889 and
jestjs/jest#11438

I haven't made any efforts to change the `update` function to write
updates to the loaded files, as this would be difficult/impossible to
update something like a .js or .yml (if using features like anchors) in
a meaningful way.

A few notes on the other changes included:
1. `cosmiconfig` pulls in a newer version of TypeScript which was
incompatible with the version of `@types/node` we used, updated it
2. One of the tests produced invalid JSON to a config file, which failed
silently before and passed the test, but now fails loudly when
`cosmiconfig` tries to read and parse the JSON. Updated it to be valid
to fulfill the spirit of the test.

---------

Co-authored-by: Stephan Meijer <stephan.meijer@gmail.com>

package.json

@@ -41,6 +41,7 @@
     "@typescript-eslint/parser": "^5.27.1",
     "@typescript-eslint/typescript-estree": "^5.27.1",
     "chalk": "^4.1.0",
+    "cosmiconfig": "^8.3.6",
     "debug": "^4.3.2",
     "file-entry-cache": "^6.0.1",
     "flow-remove-types": "2.156.0",

src/__tests__/cli.ts

@@ -181,6 +181,68 @@ cases(
       exitCode: 1,
       stdout: /1 unimported files.*bar.js/s,
     },
+    {
+      name: 'should support JSON config',
+      files: [
+        { name: 'package.json', content: '{}' },
+        {
+          name: '.unimportedrc.json',
+          content: '{ "entry": ["entry.js"] }',
+        },
+        { name: 'entry.js', content: `import foo from './foo';` },
+        { name: 'foo.js', content: '' },
+        { name: 'bar.js', content: '' },
+      ],
+      exitCode: 1,
+      stdout: /1 unimported files.*bar.js/s,
+    },
+    {
+      name: 'should support JS config',
+      files: [
+        { name: 'package.json', content: '{}' },
+        {
+          name: '.unimportedrc.js',
+          content: 'module.exports = { entry: ["entry.js"] }',
+        },
+        { name: 'entry.js', content: `import foo from './foo';` },
+        { name: 'foo.js', content: '' },
+        { name: 'bar.js', content: '' },
+      ],
+      exitCode: 1,
+      stdout: /1 unimported files.*bar.js/s,
+    },
+    {
+      name: 'should support YML config',
+      files: [
+        { name: 'package.json', content: '{}' },
+        {
+          name: '.unimportedrc.yml',
+          content: `
+entry:
+  - entry.js
+          `,
+        },
+        { name: 'entry.js', content: `import foo from './foo';` },
+        { name: 'foo.js', content: '' },
+        { name: 'bar.js', content: '' },
+      ],
+      exitCode: 1,
+      stdout: /1 unimported files.*bar.js/s,
+    },
+    {
+      name: 'should support package.json config',
+      files: [
+        {
+          name: 'package.json',
+          content: '{ "unimported": { "entry": ["entry.js"] } }',
+        },
+        { name: 'entry.js', content: `import foo from './foo';` },
+        { name: 'foo.js', content: '' },
+        { name: 'bar.js', content: '' },
+      ],
+      exitCode: 1,
+      stdout: /1 unimported files.*bar.js/s,
+    },
     {
       name: 'should identify unresolved imports',
       files: [
@@ -893,7 +955,7 @@ export default promise
         { name: 'helpers/index.ts', content: '' },
         {
           name: '.unimportedrc.json',
-          content: '{ "pathTransforms": { "(\\..+)\\.js$": "$1.ts" } }',
+          content: '{ "pathTransforms": { "(..+).js$": "$1.ts" } }',
         },
       ],
       exitCode: 0,

src/config.ts

@@ -1,3 +1,4 @@
+import { cosmiconfigSync } from 'cosmiconfig';
 import { ProcessedResult } from './process';
 import { readJson, writeJson } from './fs';
 import { CliArguments, Context, PackageJson } from './index';
@@ -137,9 +138,8 @@ export async function getConfig(args?: CliArguments): Promise<Config> {
     return cachedConfig;
   }
 
-  const configFile = await readJson<Partial<UnimportedConfig>>(
-    args?.config || CONFIG_FILE,
-  );
+  const cosmiconfigResult = cosmiconfigSync('unimported').search();
+  const configFile = cosmiconfigResult?.config as Partial<UnimportedConfig>;
 
   const unimportedPkg = await readPkgUp({ cwd: __dirname });