[FIX] compute the mimetype from new datas or raw to prevent errors wh…

…en the new mimetype doesn't match the old one

fs_attachment/models/ir_attachment.py

@@ -286,29 +286,33 @@ def create(self, vals_list):
 
     def write(self, vals):
         if not self:
-            return self
+            return super().write(vals)
         if ("datas" in vals or "raw" in vals) and not (
             "name" in vals or "mimetype" in vals
         ):
-            # When we write on an attachment, if the mimetype is not provided, it
-            # will be computed from the name. The problem is that if you assign a
-            # value to the field ``datas`` or ``raw``, the name is not provided
-            # nor the mimetype, so the mimetype will be set to ``application/octet-
-            # stream``.
-            # We want to avoid this, so we take the mimetype of the first attachment
-            # and we set it on all the attachments if they all have the same mimetype.
-            # If they don't have the same mimetype, we raise an error.
-            # OPW-3277070
-            mimetypes = self.mapped("mimetype")
-            if len(set(mimetypes)) == 1:
-                vals["mimetype"] = mimetypes[0]
+            mimetype = self._compute_mimetype(vals)
+            if mimetype and mimetype != "application/octet-stream":
+                vals["mimetype"] = mimetype
             else:
-                raise UserError(
-                    _(
-                        "You can't write on multiple attachments with different "
-                        "mimetypes at the same time."
+                # When we write on an attachment, if the mimetype is not provided, it
+                # will be computed from the name. The problem is that if you assign a
+                # value to the field ``datas`` or ``raw``, the name is not provided
+                # nor the mimetype, so the mimetype will be set to ``application/octet-
+                # stream``.
+                # We want to avoid this, so we take the mimetype of the first attachment
+                # and we set it on all the attachments if they all have the same mimetype.
+                # If they don't have the same mimetype, we raise an error.
+                # OPW-3277070
+                mimetypes = self.mapped("mimetype")
+                if len(set(mimetypes)) == 1:
+                    vals["mimetype"] = mimetypes[0]
+                else:
+                    raise UserError(
+                        _(
+                            "You can't write on multiple attachments with different "
+                            "mimetypes at the same time."
+                        )
                     )
-                )
         for rec in self:
             # As when creating a new attachment, we must pass the res_field
             # and res_model into the context hence sadly we must perform 1 call

fs_attachment/tests/test_fs_attachment.py

@@ -422,3 +422,37 @@ def test_create_attachments_basic_user(self):
                 "res_field": partner_image_field.name,
             }
         )
+
+    def test_update_png_to_svg(self):
+        b64_data_png = (
+            b"iVBORw0KGgoAAAANSUhEUgAAADMAAAAhCAIAAAD73QTtAAAAA3NCSVQICAjb4U/gAA"
+            b"AAP0lEQVRYhe3OMQGAMBAAsVL/nh8FDDfxQ6Igz8ycle7fgU9mnVln1pl1Zp1ZZ9aZd"
+            b"WadWWfWmXVmnVln1u2dvfL/Az+TRcv4AAAAAElFTkSuQmCC"
+        )
+
+        attachment = self.ir_attachment_model.create(
+            {
+                "name": "test.png",
+                "datas": b64_data_png,
+            }
+        )
+        self.assertEqual(attachment.mimetype, "image/png")
+
+        b64_data_svg = (
+            b"PD94bWwgdmVyc2lvbj0iMS4wIiBzdGFuZGFsb25lPSJubyI/Pgo8IURPQ1RZUEU"
+            b"gc3ZnIFBVQkxJQyAiLS8vVzNDLy9EVEQgU1ZHIDIwMDEwOTA0Ly9FTiIKICJodH"
+            b"RwOi8vd3d3LnczLm9yZy9UUi8yMDAxL1JFQy1TVkctMjAwMTA5MDQvRFREL3N2Zz"
+            b"EwLmR0ZCI+CjxzdmcgdmVyc2lvbj0iMS4wIiB4bWxucz0iaHR0cDovL3d3dy53My5"
+            b"vcmcvMjAwMC9zdmciCiB3aWR0aD0iNTEuMDAwMDAwcHQiIGhlaWdodD0iMzMuMDAw"
+            b"MDAwcHQiIHZpZXdCb3g9IjAgMCA1MS4wMDAwMDAgMzMuMDAwMDAwIgogcHJlc2Vydm"
+            b"VBc3BlY3RSYXRpbz0ieE1pZFlNaWQgbWVldCI+Cgo8ZyB0cmFuc2Zvcm09InRyYW5z"
+            b"bGF0ZSgwLjAwMDAwMCwzMy4wMDAwMDApIHNjYWxlKDAuMTAwMDAwLC0wLjEwMDAwMCk"
+            b"iCmZpbGw9IiMwMDAwMDAiIHN0cm9rZT0ibm9uZSI+CjwvZz4KPC9zdmc+Cg=="
+        )
+        attachment.write(
+            {
+                "datas": b64_data_svg,
+            }
+        )
+
+        self.assertEqual(attachment.mimetype, "image/svg+xml")