Fix Pylance settings handling on Dev18

[Stella Huang (StellaHuang95)]

Summary

Fixes #8578.

Checking Automatically add brackets to functions persisted correctly in Visual Studio, but Dev18 did not deliver the enabled setting to Pylance. As a result, Pylance continued returning plain completion text such as getcwd instead of a snippet such as getcwd($0).

Root cause

Dev18 uses System.Text.Json for eligible language clients, exposing three serialization and binding mismatches in the PTVS/Pylance configuration path:

• Pylance sends workspace/configuration parameters as one object ({ "items": [...] }), but the custom StreamJsonRpc handler did not opt into whole-object parameter binding, so the request was rejected with -32602.
• PTVS's outbound settings DTO used public fields. System.Text.Json does not serialize those fields by default, so the settings payload became {} even when the option was enabled.
• The fallback workspace/didChangeConfiguration payload placed analysis settings directly under settings.analysis, while Pylance expects the section under settings.python.analysis.

Latest main also introduced a JToken signature-help middle layer. On Dev18, that type selects the Newtonsoft formatter for the whole language client, which conflicts with the STJ-compatible path needed for PTVS's initialize interception. The Dev18 implementation therefore uses JsonDocument, while the existing Dev17 JToken implementation remains unchanged.

Fix

• Enable whole-object binding for object-shaped custom RPC messages, including workspace/configuration.
• Deserialize custom payloads through a serializer-neutral helper that accepts both Newtonsoft and Dev18 STJ values.
• Convert outbound Pylance settings fields to properties so both serializers emit the same JSON contract.
• Send fallback configuration under the required python section.
• Keep Dev18 signature-help interception on the System.Text.Json middle-layer contract while preserving the prior Dev17 path.
• Align the custom Pylance progress notification handler signatures with their protocol shapes.

Risk

Risk is low because the changes are limited to the Pylance language-client serialization and custom RPC boundary:

• Wire names and setting values are unchanged; the settings that were previously omitted are now serialized.
• Whole-object binding is applied only to methods whose protocol parameters are object-shaped.
• The fallback envelope now matches Pylance's documented section lookup.
• Dev17 retains its existing signature-help implementation through conditional compilation.
• Completion insertion behavior is not changed; this only allows Pylance to receive the existing option and return the intended snippet.

Validation

The fix was manually verified on Dev18: after enabling the option, function completions included parentheses as expected. No tests were added for this change.

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[Heejae Chang (heejaechang)]

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[Stella Huang (StellaHuang95)]

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Pull request overview

This pull request fixes Dev18 (System.Text.Json-based) configuration delivery to Pylance so that VS options (notably Automatically add brackets to functions) are correctly serialized/bound and reflected in Pylance completion behavior.

Changes:

• Updated Dev18 signature-help interception to use a System.Text.Json-friendly contract (JsonDocument) while preserving the Dev17 JToken path.
• Enabled whole-object parameter binding for object-shaped custom JSON-RPC messages and added a cross-serializer deserialization helper.
• Updated settings payload shape/serialization (DTO fields → properties; fallback didChangeConfiguration now sends settings under the python section key).

Show a summary per file

File	Description
Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonSignatureHelpMiddleLayer.cs	Switches Dev18 middle-layer generic to JsonDocument to avoid Newtonsoft selecting the wrong formatter.
Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs	Adjusts JSON-RPC handlers to use single-object parameter binding and serializer-neutral deserialization.
Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClient.cs	Updates fallback didChangeConfiguration payload to be section-keyed under python.
Python/Product/PythonTools/PythonTools/LanguageServerClient/LanguageServerSettings.cs	Converts outbound settings DTO public fields to properties so STJ and Newtonsoft serialize consistently.

Review details

Comments suppressed due to low confidence (2)

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:175

• OnWorkspaceConfiguration no longer catches exceptions. If Deserialize(...) or the WorkspaceConfiguration event handler throws, the exception can bubble out of the JSON-RPC target and potentially disrupt the language-client RPC loop; the previous implementation returned null on failure.

        public async Task<object> OnWorkspaceConfiguration(object arg) {
            var reqParams = Deserialize<WorkspaceConfiguration.ConfigurationParams>(arg);
            if (this.WorkspaceConfiguration != null && reqParams != null) {
                var eventArgs = new ConfigurationArgs { requestParams = reqParams, requestResult = null };
                await this.WorkspaceConfiguration.InvokeAsync(this, eventArgs);

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:190

• Deserialize<T> relies on arg.ToString() to produce JSON for non-JToken values. For System.Text.Json payloads this is not guaranteed (e.g., JsonDocument.ToString() is not JSON), which can cause deserialization failures and break configuration/registration handling.

            // Dev18 supplies System.Text.Json values; older formatters supply JToken.
            return arg is JToken token
                ? token.ToObject<T>()
                : JsonConvert.DeserializeObject<T>(arg.ToString());
        }

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Low

[Stella Huang (StellaHuang95)]

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Review details

Comments suppressed due to low confidence (2)

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:190

• Deserialize falls back to JsonConvert.DeserializeObject(arg.ToString()) for System.Text.Json payloads. If StreamJsonRpc supplies a JsonDocument (or other STJ container that doesn’t override ToString()), arg.ToString() won’t be valid JSON, causing deserialization to fail (and silently break telemetry/config handling). Prefer extracting raw JSON via GetRawText() for JsonElement/JsonDocument before passing to JsonConvert.

            // Dev18 supplies System.Text.Json values; older formatters supply JToken.
            return arg is JToken token
                ? token.ToObject<T>()
                : JsonConvert.DeserializeObject<T>(arg.ToString());
        }

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:116

• OnTelemetryEvent previously swallowed all exceptions during logging/notification handling. The new implementation can let exceptions from Trace/_logger/PylanceException (or event handlers) bubble out of the JsonRpc dispatch, which can destabilize the LSP connection. Consider restoring a defensive try/catch around the logging + AnalysisComplete notification (and fix the current mis-indentation on the invoke line).

            Trace.WriteLine(arg);
            if (telemetry.Exception == null) {
                _logger?.LogEvent(telemetry.EventName, telemetry.Properties, telemetry.Measurements);
            } else {
                _logger?.LogFault(new PylanceException(telemetry.EventName, telemetry.Exception.stack), telemetry.EventName, false);

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Low

[Heejae Chang (heejaechang)]

Approved via Review Center.

[Stella Huang (StellaHuang95)]

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Review details

Comments suppressed due to low confidence (3)

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:116

• OnTelemetryEvent no longer guards the logging/event-invocation block with a catch. If a logger implementation or an AnalysisComplete subscriber throws, the exception can escape the JSON-RPC target and potentially tear down the RPC connection. Wrap the processing block in a try/catch (matching the prior behavior) so malformed/unexpected telemetry can’t destabilize the client.

            Trace.WriteLine(arg);
            if (telemetry.Exception == null) {
                _logger?.LogEvent(telemetry.EventName, telemetry.Properties, telemetry.Measurements);
            } else {
                _logger?.LogFault(new PylanceException(telemetry.EventName, telemetry.Exception.stack), telemetry.EventName, false);

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:144

• Changing python/endProgress to a parameterless method can cause JSON-RPC binding failures (-32602) if the server sends a params object (even an empty one). Consider taking a single optional parameter to remain compatible with both shapes.

        [JsonRpcMethod("python/endProgress")]
        public async Task OnEndProgressAsync() {
            await _joinableTaskContext.Factory.SwitchToMainThreadAsync();

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:175

• OnWorkspaceConfiguration previously swallowed deserialization/handler exceptions and returned null. The new implementation can now throw (e.g., JsonException from Deserialize or exceptions from WorkspaceConfiguration handlers), which risks breaking the JSON-RPC connection. Reintroduce a catch and return null on failure, similar to OnWorkspaceFolders.

        [JsonRpcMethod("workspace/configuration", UseSingleObjectParameterDeserialization = true)]
        public async Task<object> OnWorkspaceConfiguration(object arg) {
            var reqParams = Deserialize<WorkspaceConfiguration.ConfigurationParams>(arg);
            if (this.WorkspaceConfiguration != null && reqParams != null) {
                var eventArgs = new ConfigurationArgs { requestParams = reqParams, requestResult = null };
                await this.WorkspaceConfiguration.InvokeAsync(this, eventArgs);

• Files reviewed: 6/6 changed files
• Comments generated: 3
• Review effort level: Low

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Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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[Heejae Chang (heejaechang)]

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