[XSG] Improve diagnostic reporting during binding compilation by Copilot · Pull Request #32905 · dotnet/maui

Copilot · 2025-11-28T12:41:07Z

Original prompt

This section details on the original issue you should resolve

<issue_title>[XSG] Improve diagnostic reporting during binding compilation</issue_title>
<issue_description>We left several todos in the binding compilation logic in the XAML source generator. We should try to match the warnings and errors produced by XamlC, just with an adjusted error code.</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes [XSG] Improve diagnostic reporting during binding compilation #32904

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

simonrozsival

@copilot make these changes

src/Controls/src/SourceGen/TypeConverters/ColumnDefinitionCollectionConverter.cs

src/Controls/src/SourceGen/Descriptors.cs

src/Controls/src/SourceGen/AnalyzerReleases.Unshipped.md

simonrozsival · 2025-11-28T16:21:58Z

/azp run

azure-pipelines · 2025-11-28T16:22:19Z

Azure Pipelines successfully started running 3 pipeline(s).

Copilot

Pull request overview

This PR improves diagnostic reporting in the XAML source generator by replacing TODO comments and exception throws with proper diagnostic reporting that matches XamlC error codes. The changes enable developers to receive clear, actionable error and warning messages during XAML compilation.

Key Changes:

Adds 6 new diagnostics (MAUIX2024, MAUIX2041-MAUIX2043, MAUIX2045, MAUIX2064) that correspond to XamlC error codes
Replaces return false; // TODO report diagnostic statements with proper diagnostic calls in binding compilation
Replaces throw new Exception("dup x:Name") with diagnostic reporting for duplicate name detection
Includes 4 unit tests validating the new diagnostic scenarios (though 2 diagnostics lack test coverage)

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Controls/src/SourceGen/CompiledBindingMarkup.cs	Replaces TODO comments with diagnostic reporting for binding compilation errors (indexer issues, property not found, unsupported types)
src/Controls/src/SourceGen/Descriptors.cs	Adds 6 new DiagnosticDescriptor definitions with appropriate IDs, severities, and localized messages
src/Controls/src/SourceGen/MauiGResources.resx	Adds localized resource strings for the new diagnostics with clear, user-friendly messages
src/Controls/src/SourceGen/xlf/MauiGResources.Designer.cs	Auto-generated designer file adding strongly-typed properties for accessing the new resource strings
src/Controls/src/SourceGen/KnownMarkups.cs	Replaces x:DataType outer scope TODO with proper warning diagnostic and includes minor whitespace formatting improvements
src/Controls/src/SourceGen/Visitors/SetNamescopesAndRegisterNames.cs	Replaces exception throw for duplicate x:Name with diagnostic reporting
src/Controls/src/SourceGen/AnalyzerReleases.Unshipped.md	Documents the 6 new diagnostics being added
src/Controls/tests/SourceGen.UnitTests/BindingDiagnosticsTests.cs	Adds 4 new unit tests validating diagnostic reporting for property not found, indexer errors, and duplicate names

Files not reviewed (1)

src/Controls/src/SourceGen/xlf/MauiGResources.Designer.cs: Language not supported

src/Controls/src/SourceGen/CompiledBindingMarkup.cs

src/Controls/tests/SourceGen.UnitTests/BindingDiagnosticsTests.cs

simonrozsival · 2025-11-28T17:33:12Z

/azp run

azure-pipelines · 2025-11-28T17:33:32Z

Azure Pipelines successfully started running 3 pipeline(s).

simonrozsival · 2025-12-01T08:38:55Z

/azp run

azure-pipelines · 2025-12-01T08:39:17Z

Azure Pipelines successfully started running 3 pipeline(s).

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Downgrade MAUIG2041 (BindingIndexerNotClosed), MAUIG2042 (BindingIndexerEmpty), MAUIG2043 (BindingIndexerTypeUnsupported), and MAUIG2045 (BindingPropertyNotFound) from Error to Warning severity. This allows builds to succeed while still notifying developers of binding issues that will fall back to reflection-based bindings at runtime.

This reverts commit 45641cf.

Modified SourceGenContext.ReportDiagnostic to check the NoWarn metadata from XAML files and suppress matching diagnostic IDs. This allows per-file suppression of source generator diagnostics (like MAUIG2043 and MAUIG2045). Added NoWarn entries for XAML unit test files that intentionally have invalid bindings to test fallback to reflection-based bindings. Also fixed Maui32879Tests to include the #pragma warning disable CS0219 line that was added in recent changes.

…pported test

…ding errors

The BindingPropertyNotFound diagnostic is now a Warning instead of Error because the MAUI source generator cannot always see properties generated by other source generators (e.g., CommunityToolkit.Mvvm's [ObservableProperty] or custom bindable property generators). While this diagnostic might indicate a typo in the binding path, it could also be a valid property that will exist at runtime but is not visible during the MAUI XAML compilation phase due to source generator execution ordering. When this warning occurs: - The binding compilation falls back to reflection-based binding (slower) - The binding will work correctly at runtime if the property exists - Users are informed that the property might be source-generated - Users are encouraged to report issues to help improve interoperability Changes: - Updated Descriptors.cs: Error -> Warning severity with explanatory comments - Updated MauiGResources.resx: Enhanced message to explain the limitation - Updated AnalyzerReleases.Unshipped.md: Reflected severity change - Updated test expectations: DiagnosticSeverity.Error -> Warning - Removed NoWarn entries: No longer needed since it's a warning - Added inline comments explaining the reasoning in code

- [x] Analyze the issue - understand TODOs in binding compilation logic - [x] Identify files to modify: `CompiledBindingMarkup.cs`, `KnownMarkups.cs`, `Descriptors.cs`, `MauiGResources.resx`, etc. - [x] Build and test baseline (100 tests passing) - [x] Add new diagnostic descriptors for binding-related errors (matching XamlC error codes) - MAUIG2041: BindingIndexerNotClosed (matching XC0041) - MAUIG2042: BindingIndexerEmpty (matching XC0042) - MAUIG2043: BindingIndexerTypeUnsupported (matching XC0043) - MAUIG2045: BindingPropertyNotFound (matching XC0045) - MAUIG2024: BindingWithXDataTypeFromOuterScope warning (matching XC0024) - MAUIG2064: NamescopeDuplicate (matching XC0064) - [x] Replace `return false; // TODO report diagnostic` with actual diagnostic reporting - [x] Replace `throw new Exception` with diagnostic reporting - [x] Update resource strings to match XamlC messages - [x] Add unit tests for the new diagnostics (6 tests) - [x] Update AnalyzerReleases.Unshipped.md - [x] Build and test (147 tests passing) - [x] Run code review and address feedback - [x] Run CodeQL checker (no security issues found) - [x] Revert unrelated formatting changes - [x] Fix alignment in Descriptors.cs - [x] Change diagnostic prefix from MAUIX to MAUIG per reviewer feedback - [x] Remove unreachable code in CompiledBindingMarkup.cs - [x] Add missing test scenarios for MAUIG2024 and MAUIG2043 diagnostics - [x] Support NoWarn metadata for source generator diagnostics - [x] Add MAUIG2045 to NoWarn for test XAML files with intentional binding errors - [x] Address latest code review feedback: - Refactored repeated indexer lookup pattern into reusable local function - Removed localized message checks from diagnostic tests - Fixed IndexerBindings test assertions to properly validate lambda context using regex patterns that match actual generated code structure  <details> <summary>Original prompt</summary> > > ---- > > *This section details on the original issue you should resolve* > > <issue_title>[XSG] Improve diagnostic reporting during binding compilation</issue_title> > <issue_description>We left several todos in the binding compilation logic in the XAML source generator. We should try to match the warnings and errors produced by XamlC, just with an adjusted error code.</issue_description> > > ## Comments on the Issue (you are @copilot in this section) > > <comments> > </comments> > </details> - Fixes #32904  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com> Co-authored-by: Simon Rozsival <simon@rozsival.com>

@HarishwaranVijayakumar

## What's Coming .NET MAUI inflight/candidate introduces significant improvements across all platforms with focus on quality, performance, and developer experience. This release includes 16 commits with various improvements, bug fixes, and enhancements. ## Checkbox - [Android] Implement material3 support for CheckBox by @HarishwaranVijayakumar in #33339 <details> <summary>🔧 Fixes</summary> - [Implement Material3 Support for CheckBox](#33338) </details> ## CollectionView - [Android] Fixed EmptyView doesn’t display when CollectionView is placed inside a VerticalStackLayout by @NanthiniMahalingam in #33134 <details> <summary>🔧 Fixes</summary> - [CollectionView does not show an EmptyView template with an empty collection](#32932) </details> ## Essentials - [Windows]Fix NullReferenceException in OpenReadAsync for FileResult created with full path by @devanathan-vaithiyanathan in #28238 <details> <summary>🔧 Fixes</summary> - [[Windows] FileResult(string fullPath) not initialized properly](#26858) </details> ## Image - Fix Glide IllegalArgumentException in MauiCustomTarget.clear() for destroyed activities by @jfversluis via @Copilot in #29780 <details> <summary>🔧 Fixes</summary> - [java.lang.IllegalArgumentException: You cannot start a load for a destroyed activity - glide](#29699) </details> ## Label - [Android] Fix for Label WordWrap width issue causing HorizontalOptions misalignment by @praveenkumarkarunanithi in #33281 <details> <summary>🔧 Fixes</summary> - [[Android] Unexpected Line Breaks in Android, Label with WordWrap Mode Due to Trailing Space.](#31782) - [Label not sized correctly on Android](#27614) </details> - Fix to Improve Flyout Accessibility by Adjusting UITableViewController Labels by @SuthiYuvaraj in #31619 <details> <summary>🔧 Fixes</summary> - [Navigation section present under hamburger are programmatically define as table :A11y_.NET maui_User can get all the insights of Dashboard_Devtools](#30894) </details> ## Mediapicker - [Regression][iOS] Fix MediaPicker PickPhotosAsync getting file name in contentType property by @devanathan-vaithiyanathan in #33390 <details> <summary>🔧 Fixes</summary> - [[iOS] MediaPicker PickPhotosAsync getting file name in contentType property](#33348) </details> ## Navigation - Fix handler not disconnected when removing non visible pages using RemovePage() by @Vignesh-SF3580 in #32289 <details> <summary>🔧 Fixes</summary> - [NavigationPage.Navigation.RemovePage() fails to disconnect handlers when removing pages, unlike ContentPage.Navigation.RemovePage()](#32239) </details> ## Picker - [Android] Fix Picker IsOpen not reset when picker is dismissed by @devanathan-vaithiyanathan in #33332 <details> <summary>🔧 Fixes</summary> - [[Android] Picker IsOpen not reset when picker is dismissed](#33331) </details> ## Shell - [iOS & Catalyst ] Fixed IsEnabled property should work on Tabs by @SubhikshaSf4851 in #33369 <details> <summary>🔧 Fixes</summary> - [[Catalyst] TabBarBackgroundColor, TabBarUnselectedColor, and IsEnabled Not Working as Expected in Shell](#33158) </details> - [iOS,Windows] Fix navigation bar colors not resetting when switching ShellContent by @Vignesh-SF3580 in #33228 <details> <summary>🔧 Fixes</summary> - [[iOS, Windows] Shell Navigation bar colors are not updated correctly when switching ShellContent](#33227) </details> - [iOS] Fixed Shell navigation on search handler suggestion selection by @SubhikshaSf4851 in #33406 <details> <summary>🔧 Fixes</summary> - [[iOS] Clicking on search suggestions fails to navigate to detail page correctly](#33356) </details> ## Templates - Fix VoiceOver doesnot announces the State of the ComboBox by @SuthiYuvaraj in #32286 ## Xaml - [XSG][BindingSourceGen] Add support for CommunityToolkit.Mvvm ObservablePropertyAttribute by @simonrozsival via @Copilot in #33028 <details> <summary>🔧 Fixes</summary> - [[XSG] Add heuristic to support bindable properties generated by other source generators](#32597) </details> <details> <summary>📦 Other (2)</summary> - [XSG] Improve diagnostic reporting during binding compilation by @simonrozsival via @Copilot in #32905 - [Testing] Fixed Test case failure in PR 33574 - [01/19/2026] Candidate - 1 by @TamilarasanSF4853 in #33602 </details> **Full Changelog**: main...inflight/candidate

Copilot AI assigned Copilot and simonrozsival Nov 28, 2025

Copilot started work on behalf of simonrozsival November 28, 2025 12:41 View session

Copilot AI changed the title ~~[WIP] Improve diagnostic reporting during binding compilation~~ [XSG] Improve diagnostic reporting during binding compilation Nov 28, 2025

Copilot AI requested a review from simonrozsival November 28, 2025 13:14

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simonrozsival marked this pull request as ready for review November 28, 2025 16:22

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Copilot started work on behalf of simonrozsival November 28, 2025 16:38 View session

Copilot AI requested a review from simonrozsival November 28, 2025 16:49

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simonrozsival mentioned this pull request Dec 1, 2025

[C] Fix NullReferenceException when binding to Dictionary<Enum, object> with x:DataType #32916

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StephaneDelcroix added this to the .NET 10.0 SR3 milestone Dec 1, 2025

StephaneDelcroix previously approved these changes Dec 1, 2025

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PureWeen force-pushed the inflight/current branch from ba47df7 to 0fae51c Compare January 13, 2026 23:37

Copilot AI and others added 13 commits January 14, 2026 16:06

Initial plan

38f07c2

Improve diagnostic reporting in binding compilation logic

f2c9816

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Address code review feedback

1b3724e

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Change diagnostic prefix from MAUIX to MAUIG and remove unreachable code

546374f

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Add missing test scenarios for MAUIG2024 and MAUIG2043 diagnostics

314002f

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Revert "Change binding diagnostics severity from Error to Warning"

24ff9d3

This reverts commit 45641cf.

Fix indexer bindings and correct MAUIG2045 severity to Error

52eb3d9

Fix MAUIG2024 diagnostic reporting and correct BindingIndexerTypeUnsu…

5758764

…pported test

Add MAUIG2045 to NoWarn list for test XAML files with intentional bin…

e2428d3

…ding errors

Fix alignment

6f682dd

PureWeen force-pushed the copilot/improve-diagnostic-reporting branch from 5a8f59e to 6f682dd Compare January 14, 2026 22:07

PureWeen merged commit 25d8d82 into inflight/current Jan 14, 2026
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PureWeen deleted the copilot/improve-diagnostic-reporting branch January 14, 2026 22:17

github-project-automation bot moved this from Approved to Done in MAUI SDK Ongoing Jan 14, 2026

PureWeen mentioned this pull request Jan 23, 2026

January 19th, Candidate #33574

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[XSG] Improve diagnostic reporting during binding compilation#32905

[XSG] Improve diagnostic reporting during binding compilation#32905
PureWeen merged 13 commits intoinflight/currentfrom
copilot/improve-diagnostic-reporting

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