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author | Alyssa Ross <hi@alyssa.is> | 2019-01-07 02:18:36 +0000 |
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committer | Alyssa Ross <hi@alyssa.is> | 2019-01-07 02:18:47 +0000 |
commit | 36f56d99fa0a0765c9f1de4a5f17a9b05830c3f2 (patch) | |
tree | b3faaf573407b32aa645237a4d16b82778a39a92 /nixpkgs/lib/asserts.nix | |
parent | 4e31070265257dc67d120c27e0f75c2344fdfa9a (diff) | |
parent | abf060725d7614bd3b9f96764262dfbc2f9c2199 (diff) | |
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Add 'nixpkgs/' from commit 'abf060725d7614bd3b9f96764262dfbc2f9c2199'
git-subtree-dir: nixpkgs git-subtree-mainline: 4e31070265257dc67d120c27e0f75c2344fdfa9a git-subtree-split: abf060725d7614bd3b9f96764262dfbc2f9c2199
Diffstat (limited to 'nixpkgs/lib/asserts.nix')
-rw-r--r-- | nixpkgs/lib/asserts.nix | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/nixpkgs/lib/asserts.nix b/nixpkgs/lib/asserts.nix new file mode 100644 index 000000000000..8a5f1fb3feb7 --- /dev/null +++ b/nixpkgs/lib/asserts.nix @@ -0,0 +1,44 @@ +{ lib }: + +rec { + + /* Print a trace message if pred is false. + Intended to be used to augment asserts with helpful error messages. + + Example: + assertMsg false "nope" + => false + stderr> trace: nope + + assert (assertMsg ("foo" == "bar") "foo is not bar, silly"); "" + stderr> trace: foo is not bar, silly + stderr> assert failed at … + + Type: + assertMsg :: Bool -> String -> Bool + */ + # TODO(Profpatsch): add tests that check stderr + assertMsg = pred: msg: + if pred + then true + else builtins.trace msg false; + + /* Specialized `assertMsg` for checking if val is one of the elements + of a list. Useful for checking enums. + + Example: + let sslLibrary = "libressl" + in assertOneOf "sslLibrary" sslLibrary [ "openssl" "bearssl" ] + => false + stderr> trace: sslLibrary must be one of "openssl", "bearssl", but is: "libressl" + + Type: + assertOneOf :: String -> ComparableVal -> List ComparableVal -> Bool + */ + assertOneOf = name: val: xs: assertMsg + (lib.elem val xs) + "${name} must be one of ${ + lib.generators.toPretty {} xs}, but is: ${ + lib.generators.toPretty {} val}"; + +} |