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2099ebdf59
Along the lines of `assertOneOf`, but expects a list of values to be compared. This gives a good error message and is useful for lists of values, like `supportedGhcVersions` in the arguments of `haskell-language-server`.
83 lines
2.5 KiB
Nix
83 lines
2.5 KiB
Nix
{ lib }:
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rec {
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/* Throw if pred is false, else return pred.
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Intended to be used to augment asserts with helpful error messages.
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Example:
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assertMsg false "nope"
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stderr> error: nope
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assert assertMsg ("foo" == "bar") "foo is not bar, silly"; ""
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stderr> error: foo is not bar, silly
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Type:
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assertMsg :: Bool -> String -> Bool
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*/
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# TODO(Profpatsch): add tests that check stderr
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assertMsg =
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# Predicate that needs to succeed, otherwise `msg` is thrown
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pred:
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# Message to throw in case `pred` fails
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msg:
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pred || builtins.throw msg;
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/* Specialized `assertMsg` for checking if `val` is one of the elements
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of the list `xs`. Useful for checking enums.
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Example:
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let sslLibrary = "libressl";
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in assertOneOf "sslLibrary" sslLibrary [ "openssl" "bearssl" ]
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stderr> error: sslLibrary must be one of [
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stderr> "openssl"
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stderr> "bearssl"
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stderr> ], but is: "libressl"
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Type:
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assertOneOf :: String -> ComparableVal -> List ComparableVal -> Bool
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*/
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assertOneOf =
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# The name of the variable the user entered `val` into, for inclusion in the error message
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name:
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# The value of what the user provided, to be compared against the values in `xs`
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val:
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# The list of valid values
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xs:
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assertMsg
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(lib.elem val xs)
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"${name} must be one of ${
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lib.generators.toPretty {} xs}, but is: ${
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lib.generators.toPretty {} val}";
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/* Specialized `assertMsg` for checking if every one of `vals` is one of the elements
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of the list `xs`. Useful for checking lists of supported attributes.
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Example:
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let sslLibraries = [ "libressl" "bearssl" ];
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in assertEachOneOf "sslLibraries" sslLibraries [ "openssl" "bearssl" ]
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stderr> error: each element in sslLibraries must be one of [
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stderr> "openssl"
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stderr> "bearssl"
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stderr> ], but is: [
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stderr> "libressl"
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stderr> "bearssl"
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stderr> ]
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Type:
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assertEachOneOf :: String -> List ComparableVal -> List ComparableVal -> Bool
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*/
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assertEachOneOf =
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# The name of the variable the user entered `val` into, for inclusion in the error message
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name:
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# The list of values of what the user provided, to be compared against the values in `xs`
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vals:
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# The list of valid values
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xs:
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assertMsg
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(lib.all (val: lib.elem val xs) vals)
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"each element in ${name} must be one of ${
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lib.generators.toPretty {} xs}, but is: ${
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lib.generators.toPretty {} vals}";
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}
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