fix: do not allow to upload files with invalid formats

src/__tests__/upload.js

@@ -163,3 +163,55 @@ test('should call onChange/input bubbling up the event when a file is selected',
   expect(onInputInput).toHaveBeenCalledTimes(1)
   expect(onInputForm).toHaveBeenCalledTimes(1)
 })
+
+test('should upload file with accepted format', () => {
+  const file = new File(['hello'], 'hello.png', {type: 'image/png'})
+  const {element} = setup('<input type="file" accept="image/png" />')
+
+  userEvent.upload(element, file)
+
+  expect(element.files).toHaveLength(1)
+})
+
+test('should upload multiple files with accepted format', () => {
+  const files = [
+    new File(['hello'], 'hello.png', {type: 'image/png'}),
+    new File(['there'], 'there.jpg', {type: 'audio/mp3'}),
+    new File(['there'], 'there.csv', {type: 'text/csv'}),
+    new File(['there'], 'there.jpg', {type: 'video/mp4'}),
+  ]
+  const {element} = setup(`
+    <input 
+      type="file" 
+      accept="image/*,audio/*,text/csv" multiple 
+    />
+  `)
+
+  userEvent.upload(element, files)
+
+  expect(element.files).toHaveLength(3)
+})
+
+test('should not upload file with unaccepted format', () => {
+  const file = new File(['hello'], 'hello.png', {type: 'image/png'})
+  const {element} = setup('<input type="file" accept="image/jpg" />')
+
+  userEvent.upload(element, file)
+
+  expect(element.files).toHaveLength(0)
+})
+
+test('should not upload multiple files with unaccepted formats', () => {
+  const files = [
+    new File(['hello'], 'hello.txt', {type: 'text/plain'}),
+    new File(['there'], 'there.pdf', {type: 'application/pdf'}),
+    new File(['there'], 'there.png', {type: 'image/png'}),
+  ]
+  const {element} = setup(`
+    <input id="files" type="file" accept="video/*" multiple />
+  `)
+
+  userEvent.upload(element, files)
+
+  expect(element.files).toHaveLength(0)
+})

src/upload.js

@@ -10,16 +10,20 @@ function upload(element, fileOrFiles, init) {
 
   const input = element.tagName === 'LABEL' ? element.control : element
 
-  const files = (Array.isArray(fileOrFiles)
-    ? fileOrFiles
-    : [fileOrFiles]
-  ).slice(0, input.multiple ? undefined : 1)
+  const files = (Array.isArray(fileOrFiles) ? fileOrFiles : [fileOrFiles])
+    .filter(file => isAcceptableFile(file, element.accept))
+    .slice(0, input.multiple ? undefined : 1)
 
   // blur fires when the file selector pops up
   blur(element, init)
   // focus fires when they make their selection
   focus(element, init)
 
+  // treat empty array as if the user just closed the file upload dialog
+  if (files.length === 0) {
+    return
+  }
+
   // the event fired in the browser isn't actually an "input" or "change" event
   // but a new Event with a type set to "input" and "change"
   // Kinda odd...
@@ -46,4 +50,22 @@ function upload(element, fileOrFiles, init) {
   })
 }
 
+function isAcceptableFile(file, accept) {
+  if (!accept) {
+    return true
+  }
+
+  const wildcards = ['audio/*', 'image/*', 'video/*']
+
+  return accept.split(',').some(acceptToken => {
+    if (acceptToken[0] === '.') {
+      // tokens starting with a dot represent a file extension
+      return file.name.endsWith(accept)
+    } else if (wildcards.includes(acceptToken)) {
+      return file.type.startsWith(acceptToken.substr(0, acceptToken.length - 1))
+    }
+    return file.type === acceptToken
+  })
+}
+
 export {upload}