Change to make resolve sync

Browsers, deno, and now Node.js too (since v20) all use a sync resolve.
This change matches that.

This *probably* does not break code, because the following two lines are equal:

```js
const a = await 'string'
const b = 'string'
```

Closes GH-14.
Closes GH-15.

Author: giltayar

.github/workflows/main.yml

@@ -20,5 +20,5 @@ jobs:
           - ubuntu-latest
           - windows-latest
         node:
-          - lts/hydrogen
+          - 18
           - node

.gitignore

@@ -3,5 +3,5 @@
 *.log
 coverage/
 /node_modules
-test/baseline.js
+test/baseline*.js
 yarn.lock

index.js

@@ -15,11 +15,11 @@ import {defaultResolve} from './lib/resolve.js'
  * @param {string} parent
  *   The absolute parent module URL to resolve from.
  *   You should pass `import.meta.url` or something else.
- * @returns {Promise<string>}
- *   Returns a promise that resolves to a full `file:`, `data:`, or `node:` URL
+ * @returns {string}
+ *   Returns a string to a full `file:`, `data:`, or `node:` URL
  *   to the found thing.
  */
-export async function resolve(specifier, parent) {
+export function resolve(specifier, parent) {
   if (!parent) {
     throw new Error(
       'Please pass `parent`: `import-meta-resolve` cannot ponyfill that'
@@ -31,10 +31,14 @@ export async function resolve(specifier, parent) {
   } catch (error) {
     const exception = /** @type {ErrnoException} */ (error)
 
-    return exception.code === 'ERR_UNSUPPORTED_DIR_IMPORT' &&
+    if (
+      exception.code === 'ERR_UNSUPPORTED_DIR_IMPORT' &&
       typeof exception.url === 'string'
-      ? exception.url
-      : Promise.reject(error)
+    ) {
+      return exception.url
+    }
+
+    throw error
   }
 }
 

package.json

@@ -45,7 +45,7 @@
     "generate": "node --conditions development script.js",
     "build": "tsc --build --clean && tsc --build && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node --experimental-import-meta-resolve test/baseline.js && node test/index.js",
+    "test-api": "node --experimental-import-meta-resolve test/baseline.js && node --experimental-import-meta-resolve test/baseline-async.js && node test/index.js",
     "test-coverage": "c8 --check-coverage --branches 75 --functions 75 --lines 75 --statements 75 --reporter lcov npm run test-api",
     "test": "npm run generate && npm run build && npm run format && npm run test-coverage"
   },

script.js

@@ -1,10 +1,32 @@
 import path from 'node:path'
 import fs from 'node:fs/promises'
 
-const base = await fs.readFile(path.join('test', 'core.js'))
+const base = await fs.readFile(path.join('test', 'core.js'), 'utf8')
 
-const lines = String(base)
-  .replace(/\bresolve(?=\(|,)/g, 'import.meta.resolve')
-  .split('\n')
+const asyncLines = base
+  // Special baseline test for Node < 20, that doesn't support sync `import.meta.resolve`
+  .replace(/\bresolve(?=\()/g, 'await import.meta.resolve')
+  .replace(/\bresolve(?=,)/g, 'import.meta.resolve')
+  .replace(
+    /const run = .*$/g,
+    'const run = async (/** @type {() => Promise<void>} */ f) => f()'
+  )
+  .replace(/run\(/g, 'await run(async ')
 
-await fs.writeFile(path.join('test', 'baseline.js'), lines.join('\n'))
+await fs.writeFile(path.join('test', 'baseline-async.js'), asyncLines)
+
+const syncLines = base
+  // Node < 20 does not support sync import.meta.resolve, so skipping these tests if so
+  .replace(/\bresolve(?=\()/g, 'import.meta.resolve')
+  .replace(/\bresolve(?=,)/g, 'import.meta.resolve')
+  .replace(
+    '{skip: false}',
+    "{skip: semver.lt(process.versions.node, '20.0.0')}"
+  )
+  .replace(
+    /const run = .*$/g,
+    'const run = (/** @type {() => void} */ f) => f()'
+  )
+  .replace(/run\(/g, 'run(async ')
+
+await fs.writeFile(path.join('test', 'baseline.js'), syncLines)