fix: generate valid mock class names for generic interfaces with non-built-in type args

[thomhurst]

Summary

Fixes #5403

• Root cause: SanitizeIdentifier didn't handle global:: prefixes inside generic type arguments. For IFoo<SomeEnum>, the FQN global::Sandbox.IFoo<global::Sandbox.SomeEnum> had only the leading global:: stripped — inner ones survived into class names as IFoo_global::Sandbox_SomeEnum_Mock, which is invalid C#.
• Fix: Rewrote SanitizeIdentifier to use a character-based whitelist approach (letters, digits, _) that handles any special character. Also strips same-namespace qualifications from generic type arguments for cleaner names.
• Result: IFoo_SomeEnum_Mock instead of IFoo_global::Sandbox_SomeEnum_Mock

Type	Before (broken)	After
IFoo<SomeEnum>	IFoo_global::Sandbox_SomeEnum_Mock	IFoo_SomeEnum_Mock
IFoo<Bar>	IFoo_global::Sandbox_Bar_Mock	IFoo_Bar_Mock
IMapper<Entity, Status>	IMapper_global::…_Entity_global::…_Status_Mock	IMapper_Entity_Status_Mock
IService<Outer.Inner.Config>	(would contain global::)	IService_Outer_Inner_Config_Mock
IRepository<string>	IRepository_string_Mock	IRepository_string_Mock (unchanged)

Test plan

• 30/30 snapshot tests pass (5 new for enum, class, nested namespace, multiple non-built-in, nested generic type args)
• 8 new functional tests pass (end-to-end mock creation, setup, invocation, verification)
• 756/756 existing TUnit.Mocks.Tests pass (no regressions)

[codacy-production]

Not up to standards ⛔

🔴 Issues 4 minor

Alerts:
⚠ 4 issues (≤ 0 issues of at least minor severity)

Results:
4 new issues

Category	Results
BestPractice	1 minor
CodeStyle	3 minor

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🟢 Metrics 17 complexity

Metric	Results
Complexity	17

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[claude]

Code Review: fix/generic-mock-class-name-5403

Summary

Clean, well-targeted fix for #5403. The root cause diagnosis is accurate, the fix is sound, and the test coverage is excellent (5 snapshot + 8 functional tests). No blocking issues.

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The Core Fix

Old SanitizeIdentifier — chain of .Replace() calls that never stripped global:: from inner type arguments, leaving identifiers like IFoo_global::Sandbox_SomeEnum_Mock (invalid C#).

New SanitizeIdentifier — single global:: strip upfront, then a character-whitelist scan with inline double-underscore collapsing. This is strictly better: more robust, handles any special character, and is easier to reason about.

GetShortSafeName change — adds name.Replace("global::" + model.Namespace + ".", "") to strip same-namespace qualifications from generic type args. Correct and produces readable names (IFoo_SomeEnum_Mock instead of IFoo_Sandbox_SomeEnum_Mock).

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Observations

1. Trailing underscore from > is intentional (not a bug)

SanitizeIdentifier("IFoo<Bar>") produces IFoo_Bar_ (trailing _ from the >). The calling code then appends Mock directly, yielding IFoo_Bar_Mock — confirmed correct in snapshots. This is fine; just noting it since it's non-obvious.

2. Double underscore in extension class names is pre-existing

The MockMemberExtensions class names like Sandbox_IFoo_Sandbox_Bar__MockMemberExtensions have a double underscore because GetCompositeSafeName ends with _ (from >) and the appended suffix starts with _Mock. This wasn't introduced by this PR (the old code had the same trailing-underscore pattern), but it is still there. Worth a note for future cleanup if the naming convention is ever revisited.

3. Namespace-strip heuristic: potential (theoretical) collision

The replacement:

name = name.Replace("global::" + model.Namespace + ".", "");

strips all occurrences of the outer namespace prefix. This means a type in a sub-namespace also gets partially stripped — e.g., global::Sandbox.Sub.Bar → Sub.Bar when namespace is Sandbox. That produces IFoo_Sub_Bar_Mock, which is still distinct and correct.

The edge case worth noting: if two types share the same unqualified name but live in different sub-namespaces of the same outer namespace — e.g., Sandbox.Alpha.Widget and Sandbox.Beta.Widget — both strip to Widget, producing colliding mock names IFoo_Widget_Mock in the same generated namespace. This is unlikely in practice (the compiler itself would usually force disambiguation), but it's a latent correctness gap if someone has that naming structure.

A more defensive alternative would be to only strip when the type is directly in the interface's namespace (i.e., require no additional dots after stripping), but the current behaviour is probably the right trade-off for readable names.

4. System type names stay verbose

IProvider<List<Item>> → IProvider_System_Collections_Generic_List_Item_Mock. Not wrong, and consistent with keeping cross-namespace qualifications, but verbose. If there's future appetite for improving this, well-known system prefixes (System.Collections.Generic., System.Threading.Tasks., etc.) could be stripped or aliased. Out of scope for this fix, but the architecture supports it.

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Test Coverage

Snapshot tests cover all the cases described in the PR table. Functional tests exercise the full mock lifecycle (creation → setup → invocation → verification). Regression baseline of 756 existing tests passing gives high confidence.

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Verdict

Approve. The fix is correct, well-tested, and the implementation is cleaner than what it replaces. The observations above are minor and don't block merging.

[claude]

Clean, well-targeted fix. The character-whitelist SanitizeIdentifier is strictly better than the old chain of replaces, and the same-namespace stripping in GetShortSafeName correctly produces readable names. Test coverage is excellent (5 snapshot + 8 functional tests, 756 existing passing).