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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| .. | ||
| administration | ||
| configuration | ||
| development | ||
| from_md | ||
| installation | ||
| release-notes | ||
| .gitignore | ||
| contributing-to-this-manual.chapter.md | ||
| default.nix | ||
| Makefile | ||
| man-configuration.xml | ||
| man-nixos-build-vms.xml | ||
| man-nixos-enter.xml | ||
| man-nixos-generate-config.xml | ||
| man-nixos-install.xml | ||
| man-nixos-option.xml | ||
| man-nixos-rebuild.xml | ||
| man-nixos-version.xml | ||
| man-pages.xml | ||
| manual.xml | ||
| md-to-db.sh | ||
| preface.xml | ||
| README.md | ||
| shell.nix | ||