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refactor: Remove placeholder loading text and caption usage hint from streaming components. #919

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Merged
nan-yu merged 1 commit into from
Mar 24, 2026
Merged

refactor: Remove placeholder loading text and caption usage hint from streaming components. #919

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28 changes: 10 additions & 18 deletions agent_sdks/python/src/a2ui/core/parser/streaming.py
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,13 @@
"text",
}

# A safe placeholder used when referencing a child component that hasn't yet streamed in.
PLACEHOLDER_COMPONENT = {
"Row": {
"children": {"explicitList": []},
}
}


class A2uiStreamParser:
"""Parses a stream of text for A2UI JSON messages with fine-grained component yielding."""
Expand Down Expand Up @@ -1230,12 +1237,7 @@ def traverse(obj, parent_key=None):
valid_children.append(placeholder_id)
placeholder_comp = {
"id": placeholder_id,
"component": {
"Text": {
"text": {"literalString": f"Loading {child_id}..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
}
# Avoid duplicates in extra_components
if not any(ec["id"] == placeholder_id for ec in extra_components):
Expand All @@ -1253,12 +1255,7 @@ def traverse(obj, parent_key=None):
valid_children.append(placeholder_id)
placeholder_comp = {
"id": placeholder_id,
"component": {
"Text": {
"text": {"literalString": "Loading children..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
}
if not any(ec["id"] == placeholder_id for ec in extra_components):
extra_components.append(placeholder_comp)
Expand All @@ -1270,12 +1267,7 @@ def traverse(obj, parent_key=None):
obj[field] = placeholder_id
placeholder_comp = {
"id": placeholder_id,
"component": {
"Text": {
"text": {"literalString": f"Loading {child_id}..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
}
if not any(ec["id"] == placeholder_id for ec in extra_components):
extra_components.append(placeholder_comp)
Expand Down
109 changes: 30 additions & 79 deletions agent_sdks/python/tests/core/parser/test_streaming_v08.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@
MSG_TYPE_DATA_MODEL_UPDATE,
)
from a2ui.core.schema.catalog import A2uiCatalog
from a2ui.core.parser.streaming import A2uiStreamParser
from a2ui.core.parser.streaming import A2uiStreamParser, PLACEHOLDER_COMPONENT
from a2ui.core.parser.response_part import ResponsePart


Expand Down Expand Up @@ -145,6 +145,22 @@ def mock_catalog():
"Text": {"type": "object", "additionalProperties": True},
"Loading": {"type": "object", "additionalProperties": True},
"List": {"type": "object", "additionalProperties": True},
"Row": {
"type": "object",
"properties": {
"children": {
"type": "object",
"properties": {
"explicitList": {
"type": "array",
"items": {"type": "string"},
},
"required": ["componentId", "dataBinding"],
},
}
},
"required": ["children"],
},
"Column": {
"type": "object",
"properties": {
Expand Down Expand Up @@ -319,12 +335,7 @@ def test_incremental_yielding_v08(mock_catalog):
},
{
"id": "loading_children_root-column",
"component": {
"Text": {
"text": {"literalString": "Loading children..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand All @@ -345,12 +356,7 @@ def test_incremental_yielding_v08(mock_catalog):
},
{
"id": "loading_c1",
"component": {
"Text": {
"text": {"literalString": "Loading c1..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand All @@ -373,21 +379,11 @@ def test_incremental_yielding_v08(mock_catalog):
},
{
"id": "loading_c1",
"component": {
"Text": {
"text": {"literalString": "Loading c1..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
{
"id": "loading_c2",
"component": {
"Text": {
"text": {"literalString": "Loading c2..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand Down Expand Up @@ -426,12 +422,7 @@ def test_incremental_yielding_v08(mock_catalog):
},
{
"id": "loading_c2",
"component": {
"Text": {
"text": {"literalString": "Loading c2..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand Down Expand Up @@ -811,12 +802,7 @@ def test_partial_single_child_string(mock_catalog):
},
{
"id": "loading_c1",
"component": {
"Text": {
"text": {"literalString": "Loading c1..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand Down Expand Up @@ -884,12 +870,7 @@ def test_partial_template_componentId(mock_catalog):
},
{
"id": "loading_c1",
"component": {
"Text": {
"text": {"literalString": "Loading c1..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand Down Expand Up @@ -957,30 +938,15 @@ def test_partial_children_lists(mock_catalog):
},
{
"id": "loading_c1",
"component": {
"Text": {
"text": {"literalString": "Loading c1..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
{
"id": "loading_c2",
"component": {
"Text": {
"text": {"literalString": "Loading c2..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
{
"id": "loading_c3",
"component": {
"Text": {
"text": {"literalString": "Loading c3..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand Down Expand Up @@ -1013,21 +979,11 @@ def test_partial_children_lists(mock_catalog):
},
{
"id": "loading_c2",
"component": {
"Text": {
"text": {"literalString": "Loading c2..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
{
"id": "loading_c3",
"component": {
"Text": {
"text": {"literalString": "Loading c3..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
},
],
}
Expand Down Expand Up @@ -2073,12 +2029,7 @@ def test_sniff_partial_component_discards_empty_children_dict(mock_catalog):
"id": "root-column",
},
{
"component": {
"Text": {
"text": {"literalString": "Loading item-list..."},
"usageHint": "caption",
}
},
"component": PLACEHOLDER_COMPONENT,
"id": "loading_item-list",
},
],
Expand Down
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