forked from mirrors/nixpkgs
48965506a1
`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.
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| .. | ||
| systems | ||
| tests | ||
| asserts.nix | ||
| attrsets.nix | ||
| cli.nix | ||
| customisation.nix | ||
| debug.nix | ||
| default.nix | ||
| deprecated.nix | ||
| fetchers.nix | ||
| filesystem.nix | ||
| fixed-points.nix | ||
| flake.nix | ||
| generators.nix | ||
| kernel.nix | ||
| licenses.nix | ||
| lists.nix | ||
| meta.nix | ||
| minver.nix | ||
| modules.nix | ||
| options.nix | ||
| sources.nix | ||
| strings-with-deps.nix | ||
| strings.nix | ||
| trivial.nix | ||
| types.nix | ||
| versions.nix | ||
| zip-int-bits.nix | ||