[defer]

This is hilarious to me:

  Android, which uses it for some large component of the system that I've never quite understood

Ninja is really a huge part of AOSP, the build system initially used makefiles. Things got complex really fast with a custom declarative build system (soong) and a failed/aborted migration to bazel. Google developed kati (https://github.com/google/kati) which converts Makefiles to ninja build files (or should I say file), which really is huge:

  λ wc -l out/build-qssi.ninja    
    3035442 out/build-qssi.ninja

Going from makefiles/soong to ninja is painful, it takes several minutes even in a modern machine but it simply flies once ninja picks it up.

[zelphirkalt]

As someone, who has not used Ninja, what advantage is there, compared to Makefiles? And is it worth introducing yet another tool, to translate one to the other? Especially, when the Ninja files are that huge, possibly human-unreadable.

[flqn]

The Ninja files being that huge is likely more to do with the Android build environment or the tool that generates them. The main advantages of Ninja as a build executor are that the language is simple and it processes the build graph very quickly.

[defer]

They are huge because android has hundreds of smallish makefiles but the generated ninja file is a single flat file.

The advantage in android is that the different build systems will generate ninja, so they can interoperate.