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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[Stella Huang (StellaHuang95)]

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[Heejae Chang (heejaechang)]

🔒 Automated review in progress — Heejae Chang (@heejaechang) is auto-reviewing this PR.

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Pull request overview

This PR fixes Dev18 (System.Text.Json-based) configuration/serialization mismatches in the PTVS ↔ Pylance boundary so Pylance actually receives persisted settings like “Automatically add brackets to functions” and can return snippet completions (e.g., getcwd($0)) as intended.

Changes:

• Updates Dev18 signature-help interception to use JsonDocument instead of JToken to avoid forcing a Newtonsoft formatter.
• Fixes custom StreamJsonRpc handling to support whole-object parameter binding and serializer-neutral deserialization for workspace/configuration and related messages.
• Ensures Pylance settings serialize correctly under System.Text.Json by converting DTO fields to properties and nesting fallback config under settings.python.

Show a summary per file

File	Description
Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonSignatureHelpMiddleLayer.cs	Switches Dev18 middle-layer contract to JsonDocument while preserving Dev17 JToken behavior.
Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs	Adjusts custom RPC handlers to use whole-object parameter binding and adds serializer-neutral payload deserialization.
Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClient.cs	Nests fallback didChangeConfiguration payload under settings.python to match Pylance expectations.
Python/Product/PythonTools/PythonTools/LanguageServerClient/LanguageServerSettings.cs	Converts outbound settings DTO members from fields to properties so STJ emits the expected JSON.
Python/Product/PythonTools/PythonTools.csproj	Adds a Dev18-conditional reference to System.Text.Json.
Build/18.0/packages.config	Adds System.Text.Json NuGet package for Dev18 build inputs.

Review details

Comments suppressed due to low confidence (1)

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:179

• OnWorkspaceConfiguration no longer guards against deserialization failures. If Deserialize throws (malformed payload / unexpected formatter value), the RPC request will fail with an exception rather than safely returning null like the previous implementation.

        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);
                return eventArgs.requestResult;
            }
            return null;
        }

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

[Stella Huang (StellaHuang95)]

/azp run

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Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
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0.0% Coverage on New Code
0.0% Duplication on New Code

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Review details

Comments suppressed due to low confidence (1)

Python/Product/PythonTools/PythonTools/LanguageServerClient/PythonLanguageClientCustomTarget.cs:123

• The AnalysisComplete invocation is missing indentation, which makes the block harder to read and looks like a formatting slip.

            if (telemetry.EventName == "language_server/analysis_complete") {
AnalysisComplete?.Invoke(this, EventArgs.Empty);
            }

• Files reviewed: 6/6 changed files
• Comments generated: 1
• Review effort level: Low

[Heejae Chang (heejaechang)]

Approved via Review Center.

[Heejae Chang (heejaechang)]

Approved via Review Center.