[StephaneDelcroix]

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Fixes #36158

Summary

When a markup / XAML C# Expression fails to parse (e.g. a missing closing }), the source generator reported MAUIG1003: Expression must end with '}' (and the sibling MAUIG1001 parse error) at the file root (1,1) instead of the actual line/column of the offending expression.

Root cause

ExpandMarkupsVisitor.ParseExpression built the diagnostic location from an empty TextSpan / LinePositionSpan in three places (each marked //FIXME fix location), ignoring the xmlLineInfo parameter it already receives. new LinePositionSpan() defaults to line 0 / char 0, which renders as (1,1).

Fix

Derive the location from xmlLineInfo using the existing LocationHelpers.LocationCreate helper (the same helper already used throughout this file and the rest of the SourceGen), via a small CreateExpressionLocation method. It falls back gracefully to the previous behavior when line info or the relative path is unavailable.

The diagnostic now points at the expression's actual line, e.g. MainPage.xaml(33,…) instead of MainPage.xaml(1,1).

Tests

Added Maui36158Tests (in Controls.SourceGen.UnitTests) with two cases:

• The issue's exact repro — an unclosed XEPR ternary {IsActive ? 'Status: Active' : 'Status: Idle' — now reports MAUIG1003 on the expression's line.
• An unclosed markup extension {StaticResource MissingBrace — likewise reports on the correct line.

Both tests fail without the fix (reported line 0) and pass with it. The full Controls.SourceGen.UnitTests suite (218 tests) passes with no regressions.

Notes

This addresses only the diagnostic-location bug. The related issues #36157 (stale MAUIG1003 under dotnet watch), #36156 (rude-edit hot reload), and #36155 (XEPR nested-string / ternary parsing) are out of scope.

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 36165

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 36165"

[Copilot]

Pull request overview

Fixes a SourceGen diagnostic-location bug where expression/markup parse errors (e.g., missing closing }) were incorrectly reported at the file root (1,1) instead of the offending expression’s actual line/column.

Changes:

• Capture the original markup text and derive diagnostic Location from IXmlLineInfo when reporting MAUIG1003 / MAUIG1001 in ExpandMarkupsVisitor.ParseExpression.
• Add unit tests validating MAUIG1003 reports on the expression’s line (and not column 0) for both XEPR-style expressions and markup extensions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Controls/src/SourceGen/Visitors/ExpandMarkupsVisitor.cs	Uses line info to create accurate diagnostic locations for expression/markup parse errors.
src/Controls/tests/SourceGen.UnitTests/Maui36158Tests.cs	Adds regression tests asserting diagnostics point to the expression’s line/column rather than (1,1).