[FIX] web: upload file widget keep metadata fresh

When modifying files the a widget FieldMany2ManyBinaryMultiFiles would
not keep its metadata (currently associating attachment to [url,
allowUnlink]) up with current value.

So with an attachment added after init:

- clicking on it would error (because link is wrong)
- deleting it would unlink attachment originating from from onchange

The expected behavior is:

- being able to download attachments
- not unlinking attachment originating from onchange

and this is what this commit fixes.

opw-787746
closes #21813

1 files changed, 6 insertions, 4 deletions

diff --git a/addons/web/static/src/js/fields/relational_fields.js b/addons/web/static/src/js/fields/relational_fields.js
index 73e474b0342..0a8dd126570 100644
--- a/addons/web/static/src/js/fields/relational_fields.js
+++ b/addons/web/static/src/js/fields/relational_fields.js
@@ -1380,12 +1380,12 @@ var FieldMany2ManyBinaryMultiFiles = AbstractField.extend({
             throw _.str.sprintf(msg, this.field.string);
         }
 
+        this.uploadedFiles = {};
         this.uploadingFiles = [];
         this.fileupload_id = _.uniqueId('oe_fileupload_temp');
         $(window).on(this.fileupload_id, this._onFileLoaded.bind(this));
 
         this.metadata = {};
-        this._generatedMetadata();
     },
 
     destroy: function () {
@@ -1415,10 +1415,10 @@ var FieldMany2ManyBinaryMultiFiles = AbstractField.extend({
     _generatedMetadata: function () {
         var self = this;
         _.each(this.value.data, function (record) {
-            // attachments are tagged `allowUnlink` because only new attachments
-            // will be unlinked after deletion
+            // tagging `allowUnlink` ascertains if the attachment was user
+            // uploaded or was an existing or system generated attachment
             self.metadata[record.id] = {
-                allowUnlink: false,
+                allowUnlink: self.uploadedFiles[record.data.id] || false,
                 url: self._getFileUrl(record.data),
             };
         });
@@ -1430,6 +1430,7 @@ var FieldMany2ManyBinaryMultiFiles = AbstractField.extend({
     _render: function () {
         // render the attachments ; as the attachments will changes after each
         // _setValue, we put the rendering here to ensure they will be updated
+        this._generatedMetadata();
         this.$('.oe_placeholder_files, .oe_attachments')
             .replaceWith($(qweb.render('FieldBinaryFileUploader.files', {
                 widget: this,
@@ -1537,6 +1538,7 @@ var FieldMany2ManyBinaryMultiFiles = AbstractField.extend({
                 self.do_warn(_t('Uploading Error'), file.error);
             } else {
                 attachment_ids.push(file.id);
+                self.uploadedFiles[file.id] = true;
             }
         });