Files outside rootDir emit files adjacent to themselves if they are imported by an included file

Bug Report

The documentation for rootDir states that

Note that TypeScript will never write an output file to a directory outside of outDir, and will never skip emitting a file. For this reason, rootDir also enforces that all files which need to be emitted are underneath the rootDir path.

If any included file imports a ts file outside of rootDir, a declaration file is generated for that imported file and emitted adjacent to it. noEmitOnError needs to be either omitted or set to false, or the -b flag needs to be specified for this to occur.

🔎 Search Terms

noEmitOnError, unwanted declaration files, emits outside outDir, emits outside declarationDir

🕗 Version & Regression Information

On all versions matching ^4.2.4 and on the current nightly, nonexhaustive, haven't checked others

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about tsconfig.json behaviour and commandline behaviour

⏯ Playground Link

https://github.com/gtm-nayan/ts-no-emit-wat/
Sorry, couldn't figure out multiple files in the playground or the workbench.

💻 Code

🙁 Actual behavior

Declaration files emitted outside of output directory.

🙂 Expected behavior

No files should be emitted outside of the specified output directory.

首先在链接的仓库中复现该行为，重点关注 rootDir 外部的一个文件，该文件由一个被包含的文件导入，并关注由此产生的声明输出。然后追踪 TypeScript 编译器对 rootDir、outDir、declarationDir 和 noEmitOnError 的处理；完成的标准是配置的输出目录之外不会输出任何声明文件。