Python: Accept data URI parameters and default the data URI media type

python/packages/core/agent_framework/_types.py

@@ -249,17 +249,17 @@ def _validate_uri(uri: str, media_type: str | None) -> dict[str, Any]:
         if "," not in uri:
             raise ContentError("Data URI must contain a comma separating metadata and data")
         prefix, _ = uri.split(",", 1)
-        if ";" in prefix:
-            parts = prefix.split(";")
-            if len(parts) < 2:
-                raise ContentError("Invalid data URI format")
-            # Check encoding
-            encoding = parts[-1]
-            if encoding not in ("base64", ""):
-                raise ContentError(f"Unsupported data URI encoding: {encoding}")
-            if media_type is None:
-                # attempt to extract:
-                media_type = parts[0][5:]  # Remove 'data:'
+        # RFC 2397: data:[<mediatype>][;base64],<data>, where <mediatype> is type/subtype followed by
+        # optional ;attribute=value parameters. Only a final bare "base64" token names the encoding.
+        declared_type, *parameters = prefix[len("data:") :].split(";")
+        if parameters and parameters[-1] in ("base64", ""):
+            parameters = parameters[:-1]
+        for parameter in parameters:
+            if "=" not in parameter:
+                raise ContentError(f"Unsupported data URI encoding: {parameter}")
+        if media_type is None:
+            # RFC 2397 defaults an omitted media type to text/plain.
+            media_type = declared_type or "text/plain"
         return {"type": "data", "uri": uri, "media_type": media_type}
 
     # Check for common URI schemes

python/packages/core/tests/core/test_types.py

@@ -4206,6 +4206,35 @@ def test_validate_uri_data_uri():
     assert "uri" in result
 
 
+@mark.parametrize(
+    ("uri", "expected_media_type"),
+    [
+        ("data:text/plain,hello", "text/plain"),
+        ("data:text/plain;charset=utf-8,hello%20world", "text/plain"),
+        ("data:application/json;charset=utf-8;base64,e30=", "application/json"),
+        ("data:,hello", "text/plain"),
+        ("data:;base64,aGVsbG8=", "text/plain"),
+    ],
+)
+def test_validate_uri_data_uri_parameters_and_default_media_type(uri: str, expected_media_type: str):
+    """RFC 2397 data URIs may carry parameters, and the media type comes from the prefix."""
+    assert _validate_uri(uri, None) == {"type": "data", "uri": uri, "media_type": expected_media_type}
+
+
+@mark.parametrize("uri", ["data:image/png;base32,AAAA", "data:text/plain;base64;charset=utf-8,AAAA"])
+def test_validate_uri_rejects_unsupported_data_uri_encoding(uri: str):
+    """Only a final bare base64 token names an encoding; any other bare token is rejected."""
+    with raises(ContentError, match="Unsupported data URI encoding"):
+        _validate_uri(uri, None)
+
+
+def test_from_uri_accepts_data_uri_with_charset_parameter():
+    """Content.from_uri accepts a non-base64 data URI with a charset parameter."""
+    content = Content.from_uri("data:text/plain;charset=utf-8,hello%20world")
+    assert content.type == "data"
+    assert content.media_type == "text/plain"
+
+
 # endregion