2026-09-12 -- uap_scripts_commit: CS0012 on editor-only plugin DLLs

Problem (live session, RPG Maker Unite project, 2026-09-12)

uap_scripts_commit rejected a file that Unity itself compiles without error:

error CS0012: The type 'WithSerialNumberDataModel' is defined in an
assembly that is not referenced. You must add a reference to assembly
'LibForUniteForEditor, Version=1.0.0.0, ...'

The file was an Editor script under Assets/Editor/ using MapDataModel from RPGMaker.CodeBase.CoreSystem.dll. That type’s base class lives in LibForUniteForEditor.dll, an editor-platform plugin DLL under Assets/RPGMaker/Codebase/CoreSystem/LibDll/.

Two things made this look like the already-fixed 2026-08-13 CS0012 (engine modules) but it is not:

• The gate had compiled that exact file successfully several times earlier in the same session. It started failing after two unrelated .cs files were deleted from the same folder — i.e. the failure depends on what the staged compile happens to pull in, not on an edit to the file.
• referencesOptions = UseEngineModules (the 2026-08-13 fix) was already in place and is unrelated: the missing assembly here is a project plugin, not an engine module.

Measured root cause (live probe, the affected project)

Replicated the tool’s exact AssemblyBuilder setup and dumped the reference sets:

source	result
AssemblyBuilder.defaultReferences (UseEngineModules)	361 refs — contains LibForUniteForRuntime.dll, not LibForUniteForEditor.dll
CompilationPipeline.GetPrecompiledAssemblyNames()	22 names — includes LibForUniteForEditor.dll
Unity’s own Assembly-CSharp-Editor.compiledAssemblyReferences	302 refs — includes LibForUniteForEditor.dll

So AssemblyBuilder.defaultReferences carries a plugin’s RUNTIME half and drops its EDITOR half, while the predefined assembly Unity actually compiles the same file into references both. The gate was therefore strictly less capable than the Editor it is guarding, and rejected valid code.

Diffing the two sets by file name, 17 precompiled assemblies are absent from defaultReferences in this project — all editor-only plugin DLLs (LibForUniteForEditor.dll, Mono.Cecil’s editor halves, Burst’s Cecil copies, VisualScripting’s dependencies, Rider’s path locator, uloop’s Roslyn plugins).

Verification

Compiled the real failing file through the tool’s builder setup under both reference configurations, plus the two cases the 2026-08-13 note protects:

case	current refs	+ precompiled sweep
the failing Editor script	CS0012 (verbatim match with the report)	0 errors
class P : MonoBehaviour	0 errors	0 errors
class Q : UnityEngine.UI.Selectable	0 errors	0 errors

No CS0433 regression: the sweep only adds file names that are NOT already in defaultReferences, so a duplicate cannot be introduced by construction.

Fix

GatherAdditionalReferences now takes the builder’s defaultReferences and appends every CompilationPipeline.GetPrecompiledAssemblyNames() path whose file name is missing from it. additionalReferences is assigned AFTER referencesOptions, because defaultReferences is computed from it.

The UnityEditor.CoreModule entry (P1) stays. Engine references are still never added by name — that is what UseEngineModules is for.

Failure of the sweep itself (an API throw) is swallowed: the commit falls back to the previous UnityEditor-only set rather than failing.

Lesson

The gate must not be stricter than the Editor. When it rejects something, the first check should be whether Unity itself compiles the same file — here uloop control-play-mode --action Status reported CompileErrorCount: 0 for the very file the gate refused, which is what turned “my code is wrong” into “the gate is wrong” and pointed the probe at the reference set instead of the source.