gridview-templatefield-regression

name	gridview-templatefield-regression
description	Protect BWFC GridView TemplateField migrations from collapsing into BoundField output or losing nested controls
domain	migration-tooling
confidence	high
source	earned

Context

Use this when changing the Web Forms to Blazor CLI markup pipeline anywhere near GridView column transforms, template context handling, data-binding expression rewrites, or asp-prefix stripping. TemplateField preservation is a cross-transform behavior, so regressions can appear even when each individual transform still looks correct in isolation.

Patterns

• Treat TemplateField preservation as an ordered pipeline contract:
  • DisplayExpressionTransform
  • AspPrefixTransform
  • DataBindingAttributeTransform
  • AttributeStripTransform
  • GridViewColumnItemTypeTransform
  • TemplateContextTransform
• Keep regression coverage at two levels:
  1. Transform-only markup assertions through TestHelpers.CreateDefaultPipeline().
  2. Full-file migration assertions through MigrationPipeline.ExecuteAsync().
• Cover these GridView shapes explicitly:
  • TemplateField with inner TextBox
  • TemplateField with inner CheckBox
  • TemplateField with inline display expression only
  • Mixed BoundField + TemplateField siblings
  • GridView with only TemplateField columns
• Assert both preservation and non-regression:
  • Expected <TemplateField ...> count remains stable
  • Inner controls survive as BWFC components (<TextBox>, <CheckBox>)
  • ItemTemplate Context="Item" is present
  • No unexpected fallback <BoundField> appears for template-only columns

Examples

• tests/BlazorWebFormsComponents.Cli.Tests/TransformUnit/GridViewColumnItemTypeTransformTests.cs
• tests/BlazorWebFormsComponents.Cli.Tests/PipelineIntegrationTests.cs

Anti-Patterns

• Testing only GridViewColumnItemTypeTransform in isolation after changing template-related transforms.
• Verifying only the first GridView column and assuming later TemplateField siblings survived.
• Accepting output that preserves the TemplateField shell but drops nested controls or display expressions.
• Changing transform order in Program.cs without mirroring the same coverage through tests/BlazorWebFormsComponents.Cli.Tests/TestHelpers.cs.