Move [JsonConverter] from enum properties to enum types

[christianhelle]

Summary

Fixes #178 and #300 — both caused by [JsonConverter(typeof(JsonStringEnumConverter))] being placed on enum properties instead of enum types.

Root Cause

NSwag places [JsonConverter] on each property that uses an enum type. Refitter was preserving this placement (when InlineJsonConverters = true). This is semantically wrong:

• Per .NET docs, a converter in JsonSerializerOptions.Converters beats [JsonConverter] on the type but NOT on a property. So users couldn't override the converter for individual enums.
• Issue Hyphens with JsonStringEnumConverter results in JSON value could not be converted #300: Enums with hyphenated [EnumMember] values (e.g. \�llegro-pl) need a converter like JsonStringEnumMemberConverter that respects [EnumMember]. But the property-level [JsonConverter] blocked substitution via JsonSerializerOptions.

Fix

When InlineJsonConverters = true (the default), [JsonConverter(typeof(JsonStringEnumConverter))] is now placed on the enum type declaration instead of on each property. This allows users to override the converter via JsonSerializerOptions.Converters.

When InlineJsonConverters = false, behavior is unchanged: all [JsonConverter] attributes are removed.

Changes

• RefitGenerator.SanitizeGeneratedContracts: removes property-level attributes, adds type-level attribute to each public enum declaration
• CodeGeneratorSettings.InlineJsonConverters: updated XML doc to reflect new behavior
• InlineJsonConvertersTests: updated + extended tests
• HyphenatedEnumValuesTests: new test class for issue Hyphens with JsonStringEnumConverter results in JSON value could not be converted #300 scenario
• README.md: updated --no-inline-json-converters description

Tests

All 1274 tests pass. No formatting violations.

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⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 6698dcb5-f904-4911-9c20-250c89fac9cd

📥 Commits

Reviewing files that changed from the base of the PR and between fe2f428 and 1b9a76c.

📒 Files selected for processing (5)

• README.md
• src/Refitter.Core/RefitGenerator.cs
• src/Refitter.Core/Settings/CodeGeneratorSettings.cs
• src/Refitter.Tests/Examples/HyphenatedEnumValuesTests.cs
• src/Refitter.Tests/Examples/InlineJsonConvertersTests.cs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix-json-string-enum-handling

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

This PR updates Refitter’s post-processing of NSwag-generated contracts so [JsonConverter(typeof(JsonStringEnumConverter))] is applied to enum type declarations (instead of enum properties) when InlineJsonConverters = true, enabling users to override enum conversion via JsonSerializerOptions.Converters (fixing the scenarios described in #178 and #300).

Changes:

• Update RefitGenerator.SanitizeGeneratedContracts to remove property-level JsonStringEnumConverter attributes and inject a type-level attribute on public enums when inlining is enabled.
• Update InlineJsonConverters documentation (code + README) to reflect the new behavior.
• Update/extend tests and add a new regression test covering hyphenated enum values.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Refitter.Core/RefitGenerator.cs	Moves/removes JsonStringEnumConverter attributes during contract sanitization via regex.
src/Refitter.Core/Settings/CodeGeneratorSettings.cs	Updates InlineJsonConverters XML docs/description to describe type-level emission and override behavior.
src/Refitter.Tests/Examples/InlineJsonConvertersTests.cs	Adjusts assertions and adds a test ensuring converter is placed on enum type, not property.
src/Refitter.Tests/Examples/HyphenatedEnumValuesTests.cs	Adds regression tests for hyphenated enum values and converter placement.
README.md	Updates CLI option description for --no-inline-json-converters.

---

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[Copilot]

The enum-attribute insertion uses a hard-coded "\n" and a fully-qualified attribute name. This can introduce mixed line endings in otherwise CRLF output, and it also makes contracts-only / GenerateMultipleFiles output noisier because the later namespace-stripping step doesn’t run there. Consider emitting the attribute using the same line ending as the input (or Environment.NewLine) and using the non-qualified attribute/type names when the relevant using is already present.

Suggested change

	"$1[System.Text.Json.Serialization.JsonConverter(typeof(System.Text.Json.Serialization.JsonStringEnumConverter))]\n$1$2")
	"$1[System.Text.Json.Serialization.JsonConverter(typeof(System.Text.Json.Serialization.JsonStringEnumConverter))]" +
	Environment.NewLine +
	"$1$2")

[Copilot]

The negative regex assertion can miss property-level [JsonConverter] if NSwag ever emits additional attributes between [JsonConverter] and the property declaration. To make this test robust, consider matching the full attribute block for the specific property (allowing other attributes in between) or asserting that no JsonStringEnumConverter attribute appears within any property’s attribute list.

Suggested change

	// The property line itself should NOT be preceded by [JsonConverter]
	generatedCode.Should().NotMatchRegex(
	@"\[JsonConverter\(typeof\(JsonStringEnumConverter[^)]*\)\)\][\r\n\s]+public PetStatus");
	// The property line itself should NOT be preceded by [JsonConverter], even if other attributes are present
	generatedCode.Should().NotMatchRegex(
	@"\[JsonConverter\(typeof\(JsonStringEnumConverter[^)]*\)\)\](?:[\r\n\s]*\[[^\]]*\])*[\r\n\s]*public PetStatus");

[Copilot]

The regex used to assert that properties don’t have [JsonConverter] is very specific (it assumes the attribute is directly adjacent to the property declaration). If other attributes are emitted between them, the test may pass even though the property-level converter is still present. Consider broadening the regex to allow intervening attribute lines or asserting globally that no JsonStringEnumConverter attribute is applied to properties in the generated output.

Suggested change

	// Enum properties should NOT have [JsonConverter] directly on them
	generatedCode.Should().NotMatchRegex(
	@"\[JsonConverter\(typeof\(JsonStringEnumConverter[^)]*\)\)\][\r\n\s]+public \w+Id\b");
	// Enum properties should NOT have [JsonConverter] applied to them (only enum types may have it)
	generatedCode.Should().NotMatchRegex(
	@"\[JsonConverter\(typeof\(JsonStringEnumConverter[^)]*\)\)\)[\s\S]*?public\s+(?!enum)\w+\s+\w*Id\b");

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.47%. Comparing base (fe2f428) to head (1b9a76c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #938      +/-   ##
==========================================
+ Coverage   89.41%   89.47%   +0.06%     
==========================================
  Files          26       26              
  Lines        1521     1530       +9     
==========================================
+ Hits         1360     1369       +9     
  Misses         85       85              
  Partials       76       76              

Flag	Coverage Δ
unittests	89.47% <100.00%> (+0.06%)	⬆️

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