Parse complete PythonTA JSON Output

CHANGELOG.md

@@ -17,6 +17,7 @@
 
 - Updated publisher name from `<david-yz-liu>` to `david-yz-liu`
 - Fixed `substitute_attr` in the bundled language server not restoring the original value when the wrapped code raised an exception
+- Parse PythonTA's complete standard output as JSON and log an error when the output is malformed.
 
 ### 🔧 Internal changes
 

README.md

@@ -10,6 +10,10 @@ The extension checks for `.pylintrc`, `pylintrc`, and `pyproject.toml`, in that
 When project-root configuration discovery is enabled, `python-ta.configPath` is ignored. 
 When discovery is disabled, `python-ta.configPath` specifies the configuration file instead.
 
+The extension runs PythonTA with its LSP reporter and expects standard output to contain a complete
+JSON document. PythonTA error output and JSON parsing errors are available in the
+**PythonTA VS Code Extension** output channel.
+
 ## Developers
 
 ### Requirements

bundled/tool/lsp_server.py

@@ -247,12 +247,12 @@ def _linting_helper(document: workspace.Document) -> list[lsp.Diagnostic]:
 
 def _parse_json_output(content: str, doc_uri: str, use_stdin: bool = False) -> list[lsp.Diagnostic]:
     """Parses PythonTA's JSON output and maps it to LSP Diagnostics."""
-    json_start = content.find("[")
-    if json_start == -1:
+    try:
+        raw_results = json.loads(content)
+    except json.JSONDecodeError as error:
+        log_error(f"Failed to parse PythonTA output as JSON: {error}")
         return []
-    content = content[json_start:]
 
-    raw_results = json.loads(content)
     diagnostics_data = []
 
     if use_stdin:

src/test/python_tests/test_lsp_server_helpers.py

@@ -121,10 +121,15 @@ def test_parse_json_output_returns_stdin_diagnostics_despite_temporary_uri():
     assert result[0].code == "E0001"
 
 
-def test_parse_json_output_ignores_leading_log_lines():
+def test_parse_json_output_rejects_leading_log_lines(monkeypatch):
+    errors = []
+    monkeypatch.setattr(lsp_server, "log_error", errors.append)
     content = "some log preamble\nmore logs\n" + json.dumps(_make_payload())
     result = lsp_server._parse_json_output(content, "file:///home/user/project/foo.py")
-    assert len(result) == 1
+
+    assert result == []
+    assert len(errors) == 1
+    assert "Failed to parse PythonTA output as JSON" in errors[0]
 
 
 def test_parse_json_output_returns_empty_list_for_unmatched_uri():
@@ -133,8 +138,12 @@ def test_parse_json_output_returns_empty_list_for_unmatched_uri():
     assert result == []
 
 
-def test_parse_json_output_returns_empty_list_when_no_json_array_present():
+def test_parse_json_output_reports_invalid_json(monkeypatch):
+    errors = []
+    monkeypatch.setattr(lsp_server, "log_error", errors.append)
+
     assert lsp_server._parse_json_output("no json here", "file:///x.py") == []
+    assert len(errors) == 1
 
 
 def test_parse_json_output_returns_empty_list_for_file_with_no_diagnostics():