Change to remove support for errors, nullish files

lib/index.js

@@ -81,33 +81,38 @@ const labels = {
 }
 
 /**
- * Create a report from an error, one file, or multiple files.
+ * Create a report from one or more files.
  *
- * @param {Array<VFile> | Error | VFile | null | undefined} [files]
- *   Files or error to report (default: `undefined`).
+ * @param {Array<VFile> | VFile} files
+ *   Files or error to report.
  * @param {Options | null | undefined} [options]
  *   Configuration.
  * @returns {string}
  *   Report.
  */
 export function reporter(files, options) {
-  if (!files) {
-    return ''
+  const settings = options || {}
+  let one = false
+
+  if (
+    // Nothing.
+    !files ||
+    // Error.
+    ('name' in files && 'message' in files)
+  ) {
+    throw new TypeError(
+      'Unexpected value for `files`, expected one or more `VFile`s'
+    )
   }
 
-  // Error.
-  if ('name' in files && 'message' in files) {
-    return String(files.stack || files)
-  }
-
-  const options_ = options || {}
-
-  // One file.
   if (Array.isArray(files)) {
-    return format(transform(files, options_), false, options_)
+    // Empty.
+  } else {
+    one = true
+    files = [files]
   }
 
-  return format(transform([files], options_), true, options_)
+  return format(transform(files, settings), one, settings)
 }
 
 /**

readme.md

@@ -100,12 +100,12 @@ That value is also the `default` export.
 
 ### `reporter(files[, options])`
 
-Create a report from an error, one file, or multiple files.
+Create a report from one or more files.
 
 ###### Parameters
 
-*   `files` ([`Array<VFile>`][vfile], `VFile`, or `Error`, optional)
-    — files or error to report
+*   `files` ([`Array<VFile>`][vfile] or `VFile`)
+    — files to report
 *   `options` ([`Options`][api-options], optional)
     — configuration
 

test.js

@@ -57,22 +57,24 @@ test('reporter', async function () {
     'should expose `reporter` as a named and a default export'
   )
 
-  assert.equal(reporter(), '', 'should return empty without a file')
-
   assert.equal(reporter([]), '', 'should return empty when not given files')
 
-  assert.equal(reporter(exception), exception.stack, 'should support an error')
-
-  let file = new VFile({path: 'a.js'})
-
-  try {
-    file.fail('Error!')
-  } catch {}
+  assert.throws(
+    function () {
+      // @ts-expect-error: Removed support for passing nullish, which used to be supported.
+      reporter()
+    },
+    /Unexpected value for `files`, expected one or more `VFile`s/,
+    'should display a runtime error when an error is passed'
+  )
 
-  assert.equal(
-    reporter(file.messages[0]),
-    'a.js:1:1: Error!',
-    'should support a fatal message'
+  assert.throws(
+    function () {
+      // @ts-expect-error: Removed support for passing an error, which used to be supported.
+      reporter(exception)
+    },
+    /Unexpected value for `files`, expected one or more `VFile`s/,
+    'should display a runtime error when an error is passed'
   )
 
   assert.equal(
@@ -93,7 +95,7 @@ test('reporter', async function () {
     'should work on files without messages'
   )
 
-  file = new VFile({path: 'a.js'})
+  let file = new VFile({path: 'a.js'})
   file.message('Warning!')
 
   assert.equal(