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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| .. | ||
| doc | ||
| lib | ||
| maintainers | ||
| modules | ||
| tests | ||
| COPYING | ||
| default.nix | ||
| README | ||
| release-combined.nix | ||
| release-small.nix | ||
| release.nix | ||
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at https://nixos.org/nixos and in the manual in doc/manual.