FORMS-26813 : Show custom acceptMessage for unsupported file type in File Attachment (#1943)

* Fix custom accept error message not shown for unsupported file type in file input

The file-input widget's invalidMessage() looked up
constraintMessages.invalidMimeType for the unsupported-file-type alert,
but invalidMimeType is not an authorable constraint message key - the
schema only exposes constraintMessages.accept (backed by the
acceptMessage dialog property). As a result the custom message
authors configure for file type validation was always ignored in
favor of the generic fallback string, while the analogous
maxFileSize custom message worked correctly since its key matched.

Updated both the webpack source (ui.frontend) and the apps clientlib
copy (ui.af.apps) to read constraintMessages.accept, and added a
Cypress assertion mirroring the existing maxFileSize custom-message
test.

* FORMS-26813 : populate sample.afe fixture so the unsupported-type test reaches the mime-type (accept) check instead of the empty-file check

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* FORMS-26813 : use existing sample.svg fixture on fileinput3 for the unsupported-type test

Point the accept test at fileinput3 (accept=[application/pdf]) and upload sample.svg
(an image, unsupported there) instead of populating a sample.afe placeholder. svg is
non-empty so it passes the empty-file check and reaches the mime-type (accept) check.
Matches the release/650 backport (#1940).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Farha Haroon <fharoon@adobe.com>
Co-authored-by: Mayank Jindal <mayankjindal@adobe.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 4 people

it/content/src/main/content/jcr_root/content/forms/af/core-components-it/samples/fileinput/fileinputv4/basic/.content.xml

@@ -53,6 +53,7 @@
                     jcr:title="File Input - 3"
                     sling:resourceType="core/fd/components/form/fileinput/v4/fileinput"
                     accept="[application/pdf]"
+                    acceptMessage="This file type is not supported!"
                     description="This is long description"
                     fieldType="file-input"
                     id="fileinput_tooltip_scenario_test"

ui.af.apps/src/main/content/jcr_root/apps/core/fd/components/form/fileinput/v4/fileinput/clientlibs/site/js/fileinputwidget.js

@@ -191,7 +191,7 @@ if (typeof window.FileInputWidget === 'undefined') {
             const messages = {
                 [this.invalidFeature.SIZE]: customMessages.maxFileSize || FormView.LanguageUtils.getTranslatedString(this.lang, "FileSizeGreater", [fileNames, this.options.maxFileSize]),
                 [this.invalidFeature.NAME]: customMessages.invalidFileName || FormView.LanguageUtils.getTranslatedString(this.lang, "FileNameInvalid", [fileNames]),
-                [this.invalidFeature.MIMETYPE]: customMessages.invalidMimeType || FormView.LanguageUtils.getTranslatedString(this.lang, "FileMimeTypeInvalid", [fileNames]),
+                [this.invalidFeature.MIMETYPE]: customMessages.accept || FormView.LanguageUtils.getTranslatedString(this.lang, "FileMimeTypeInvalid", [fileNames]),
                 [this.invalidFeature.SIZE_ZERO]: customMessages.zeroFileSize || FormView.LanguageUtils.getTranslatedString(this.lang, "FileSizeZero", [fileNames])
             };
             return messages[invalidFeature];

ui.frontend/src/view/FormFileInputWidgetBase.js

@@ -340,7 +340,7 @@ class FormFileInputWidgetBase {
             const messages = {
                 [this.invalidFeature.SIZE]: customMessages.maxFileSize || FormView.LanguageUtils.getTranslatedString(this.lang, "FileSizeGreater", [fileName, this.options.maxFileSize]),
                 [this.invalidFeature.NAME]: customMessages.invalidFileName || FormView.LanguageUtils.getTranslatedString(this.lang, "FileNameInvalid", [fileName]),
-                [this.invalidFeature.MIMETYPE]: customMessages.invalidMimeType || FormView.LanguageUtils.getTranslatedString(this.lang, "FileMimeTypeInvalid", [fileName])
+                [this.invalidFeature.MIMETYPE]: customMessages.accept || FormView.LanguageUtils.getTranslatedString(this.lang, "FileMimeTypeInvalid", [fileName])
             };
 
             alert(messages[invalidFeature]);

ui.tests/test-module/specs/fileinput/fileinputv4.runtime.cy.js

@@ -272,6 +272,16 @@ describe('Click on button tag (V-4)', () => {
         });
     });
 
+    it('should display a custom error message configured by the user for unsupported file type', () => {
+        const [id, fieldView] = Object.entries(formContainer._fields)[2];
+        const model = formContainer._model.getElement(id);
+        const fileInput = "input[name='fileinput3']";
+        cy.attachFile(fileInput, ['sample.svg']);
+        cy.on('window:alert', (alertText) => {
+            expect(alertText).to.equal(model.getState().constraintMessages.accept);
+        });
+    });
+
     it('file when uploaded again should give actual size', () => {
         let sampleFileNames = ['sample.svg'];
         const fileInput = "input[name='fileinput2']";