compilerOptions.plugins is not inherited through tsconfig "extends"

🔎 Search Terms

extends plugins, compilerOptions.plugins extends, plugins not inherited, tsconfig extends inheritance, showConfig plugins

🕗 Version & Regression Information

• This changed between versions 6.0.3 and 7.x
• Verified against e9e477458d7b975ed5e43117fb85f6bc87363a6a

⏯ Playground Link

No response

💻 Code

tsconfig.base.json:

{ "compilerOptions": { "plugins": [{ "name": "my-plugin" }] } }

tsconfig.json:

{ "extends": "./tsconfig.base.json", "compilerOptions": { "module": "nodenext" } }

Then run tsc -p . --showConfig

🙁 Actual behavior

compilerOptions.plugins is absent from the resulting config. A plugins array declared only in a base config never reaches ParsedCommandLine.Raw, it survives only if the leaf tsconfig redeclares it.

🙂 Expected behavior

plugins is inherited from the base config, as with any other compilerOptions entry the child doesn't override (6.0.3 behaviour).

Additional information about the issue

Cause

plugins is the only declared compiler option with no field on core.CompilerOptions, it's carried purely as raw JSON. So mergeCompilerOptions never brings it across, and applyExtendedConfig's raw-JSON merge only handles include/exclude/files/contentMappers/compileOnSave.

Possibly related

root-level watchOptions looks like the same issue.

Fix

I have a fix with tests ready and am happy to open a PR.

Start with mergeCompilerOptions and applyExtendedConfig, following how compilerOptions.plugins reaches ParsedCommandLine.Raw. Reproduce the case with tsc -p . --showConfig, then add regression coverage showing that plugins from an extended tsconfig appears in the resulting configuration without being redeclared.