Simplify and modernize code style configuration (.editorconfig + .DotSettings)

[craigsmitham]

Summary

Simplify and unify code style configuration by removing redundant settings that match Roslyn defaults, adding modern C# 12/13 style rules, resolving formatting tool conflicts, and trimming .DotSettings overlap.

Background

The current .editorconfig has ~50 settings that match Roslyn defaults exactly and can be removed. Several modern C# 12/13 style rules are missing. The .DotSettings file duplicates some settings already in .editorconfig and Directory.Build.props. Additionally, dotnet format and jb cleanupcode produce different output for the same config, causing formatting churn.

Plan

Phase 1: Remove redundant settings (~50 lines)

Remove all settings where both value and severity match Roslyn defaults:

Formatting rules (all match defaults, ~30 settings):

• All 7 csharp_new_line_* settings
• All 6 csharp_indent_* settings
• All 18 csharp_space_* settings
• csharp_preserve_single_line_blocks

Code style settings matching defaults:

• dotnet_separate_import_directive_groups
• All 4 dotnet_style_parentheses_* settings
• csharp_style_expression_bodied_lambdas
• csharp_style_unused_value_expression_statement_preference

Severity consolidation: Replace ~35 rules that share the pattern "default value, elevated to :suggestion" with a single bulk severity line:

dotnet_analyzer_diagnostic.category-Style.severity = suggestion

Then only override specific rules that need warning, silent, or none.

Phase 2: Add modern C# 12/13 rules

Rule	Setting	Suggested
Primary constructors (C# 12)	csharp_style_prefer_primary_constructors	true:suggestion
Collection expressions (C# 12)	dotnet_style_prefer_collection_expression	when_types_loosely_match:suggestion
Extended property pattern (C# 10)	csharp_style_prefer_extended_property_pattern	true:suggestion
Readonly struct	csharp_style_prefer_readonly_struct	true:suggestion
Readonly struct member	csharp_style_prefer_readonly_struct_member	true:suggestion
Method group conversion	csharp_style_prefer_method_group_conversion	true:suggestion
Null check over type check	csharp_style_prefer_null_check_over_type_check	true:suggestion
Top-level statements	csharp_style_prefer_top_level_statements	true:silent

Phase 3: Resolve formatting tool conflicts

• Add targeted resharper_* settings to .editorconfig to make JB match dotnet format output for:
  • Attribute placement on enum members
  • Object/array initializer wrapping
• Use --no-builtin-settings with cleanupcode in CI
• Verify idempotency: dotnet format → jb cleanupcode → dotnet format --verify-no-changes → jb cleanupcode → git diff --exit-code

Phase 4: Trim .DotSettings

• Remove mandatory imports that duplicate Directory.Build.props <Using> items (JetBrains.Annotations, System.Diagnostics.CodeAnalysis, GraphZen.Infrastructure)
• Remove/comment ReSharper inspection severities that have .editorconfig equivalents (e.g., ConvertToCollectionExpression → IDE0300, ConvertToUsingDeclaration → IDE0063)
• Document what remains in .DotSettings and why (cleanup profile, file templates, inspection excludes)

Settings that must stay (non-default values)

Setting	Project Value	Roslyn Default
dotnet_sort_system_directives_first	true	false
csharp_style_var_* (all 3)	true	false
csharp_style_expression_bodied_methods	true	false
csharp_style_expression_bodied_constructors	true	false
csharp_style_expression_bodied_operators	true	false
csharp_style_expression_bodied_local_functions	true	false
csharp_style_namespace_declarations	file_scoped	block_scoped
csharp_preserve_single_line_statements	false	true

Verification

• dotnet format --verify-no-changes passes
• dotnet jb cleanupcode ... && git diff --exit-code passes
• dotnet build with EnforceCodeStyleInBuild=true shows no new warnings
• .editorconfig is significantly shorter with no loss of enforcement

References

• .NET code style rule options
• C# formatting options
• IDE0290: Primary constructors
• IDE0300-IDE0306: Collection expressions
• JetBrains EditorConfig index
• Configuration files for code analysis rules