Commit Graph

2 Commits

Author SHA1 Message Date
sternenseemann
48965506a1 lib/asserts: use throw to display message for assertMsg
`assert` has the annoying property that it dumps a lot of code at the
user without the built in capability to display a nicer message. We have
worked around this using `assertMsg` which would *additionally* display
a nice message. We can do even better: By using `throw` we can make
evaluation fail before assert draws its conclusions and prevent it from
displaying the code making up the assert condition, so we get the nicer
message of `throw` and the syntactical convenience of `assert`.

Before:

    nix-repl> python.override { reproducibleBuild = true; stripBytecode = false; }
    trace: Deterministic builds require stripping bytecode.
    error: assertion (((lib).assertMsg  (reproducibleBuild -> stripBytecode))  "Deterministic builds require stripping bytecode.") failed at /home/lukas/src/nix/nixpkgs/pkgs/development/interpreters/python/cpython/2.7/default.nix:45:1

After:

    nix-repl> python.override { reproducibleBuild = true; stripBytecode = false; }
    error: Deterministic builds require stripping bytecode.
2022-01-19 00:50:06 +01:00
Profpatsch
efdf618330 lib: move assertMsg and assertOneOf to their own library file
Since the `assertOneOf` uses `lib.generators`, they are not really trivial
anymore and should go into their own library file.
2018-09-06 18:14:27 +02:00