FIX: form template upload type validation (#24148)

When submitting files through the form template upload field, we were having an issue where, although a validation error message was being presented to the user, the upload was still coming through, because `PickFilesButton`'s validation happens **after** the Uppy mixin finished the upload and hit `uploadDone`.

This PR adds a new overridable method to the Uppy mixin and overrides it with the custom validation, which now happens before the file is sent.

Additionally, we're now also using `uploadingOrProcessing` as the source of truth to show the upload/uploading label, which seems more reliable.

app/assets/javascripts/discourse/app/components/form-template-field/upload.gjs

@@ -12,38 +12,51 @@ export default class FormTemplateFieldUpload extends Component.extend(
   UppyUploadMixin
 ) {
   @tracked uploadValue;
-  @tracked uploadComplete = false;
   @tracked uploadedFiles = [];
-  @tracked disabled = this.uploading;
+  @tracked disabled = this.uploadingOrProcessing;
   @tracked fileUploadElementId = `${dasherize(this.id)}-uploader`;
   @tracked fileInputSelector = `#${this.fileUploadElementId}`;
 
   type = "composer";
 
-  @computed("uploading", "uploadValue")
+  @computed("uploadingOrProcessing")
   get uploadStatusLabel() {
-    if (!this.uploading && !this.uploadValue) {
+    return this.uploadingOrProcessing
-      return "form_templates.upload_field.upload";
+      ? "form_templates.upload_field.uploading"
-    }
+      : "form_templates.upload_field.upload";
+  }
 
-    if (!this.uploading && this.uploadValue) {
+  /**
-      this.uploadComplete = true;
+   * The validation from PickFilesButton._filesPicked, where acceptedFormatsOverride
-      return "form_templates.upload_field.upload";
+   * is validated and displays a message, happens after the upload is complete.
-    }
+   *
+   * Overriding this method allows us to validate the file before the upload
+   *
+   * @param file
+   * @returns {boolean}
+   */
+  isUploadedFileAllowed(file) {
+    // same logic from PickFilesButton._hasAcceptedExtensionOrType
+    const fileTypes = this.attributes.file_types;
+    const extension = file.name.split(".").pop();
 
-    return "form_templates.upload_field.uploading";
+    return (
+      !fileTypes ||
+      fileTypes.includes(`.${extension}`) ||
+      fileTypes.includes(file.type)
+    );
   }
 
   uploadDone(upload) {
     // If re-uploading, clear the existing file if multiple aren't allowed
-    if (!this.attributes.allow_multiple && this.uploadComplete) {
+    if (!this.attributes.allow_multiple && this.uploadValue) {
       this.uploadedFiles = [];
       this.uploadValue = "";
     }
 
-    const uploadMarkdown = this.buildMarkdown(upload);
     this.uploadedFiles.pushObject(upload);
 
+    const uploadMarkdown = this.buildMarkdown(upload);
     if (this.uploadValue && this.allowMultipleFiles) {
       // multiple file upload
       this.uploadValue = `${this.uploadValue}\n${uploadMarkdown}`;

app/assets/javascripts/discourse/app/mixins/uppy-upload.js

@@ -47,6 +47,17 @@ export default Mixin.create(UppyS3Multipart, ExtendableUploader, {
     return {};
   },
 
+  /**
+   * Overridable for custom file validations, executed before uploading.
+   *
+   * @param {object} file
+   *
+   * @returns {boolean}
+   */
+  isUploadedFileAllowed() {
+    return true;
+  },
+
   uploadingOrProcessing: or("uploading", "processing"),
 
   @on("willDestroyElement")
@@ -112,7 +123,9 @@ export default Mixin.create(UppyS3Multipart, ExtendableUploader, {
           },
           this.validateUploadedFilesOptions()
         );
-        const isValid = validateUploadedFile(currentFile, validationOpts);
+        const isValid =
+          validateUploadedFile(currentFile, validationOpts) &&
+          this.isUploadedFileAllowed(currentFile);
         this.setProperties({
           uploadProgress: 0,
           uploading: isValid && this.autoStartUploads,

spec/system/composer/category_templates_spec.rb

@@ -370,6 +370,7 @@ describe "Composer Form Templates", type: :system do
     expect(find("#dialog-holder .dialog-body p", visible: :all)).to have_content(
       I18n.t("js.pick_files_button.unsupported_file_picked", { types: ".jpg, .png" }),
     )
+    expect(page).to have_no_css(".form-template-field__uploaded-files")
   end
 
   it "creates a post with multiple uploads" do
@@ -401,6 +402,22 @@ describe "Composer Form Templates", type: :system do
     )
   end
 
+  it "overrides uploaded file if allow_multiple false" do
+    topic_title = "Peter Parker's Medication"
+
+    category_page.visit(category_with_upload_template)
+    category_page.new_topic_button.click
+    attach_file "prescription-uploader",
+                "#{Rails.root}/spec/fixtures/images/logo.png",
+                make_visible: true
+    composer.fill_title(topic_title)
+    attach_file "prescription-uploader",
+                "#{Rails.root}/spec/fixtures/images/fake.jpg",
+                make_visible: true
+
+    expect(find(".form-template-field__uploaded-files")).to have_css("li", count: 1)
+  end
+
   it "shows labels and descriptions when a form template is assigned to the category" do
     category_page.visit(category_with_template_6)
     category_page.new_topic_button.click