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Merge pull request #9115 from fricklerhandwerk/lookup-algorithm

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reword documentation on lookup path resolution
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John Ericson 2023-10-10 10:44:32 -04:00 • committed by GitHub
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src/libexpr/primops.cc
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@ -1698,13 +1698,14 @@ static void prim_findFile(EvalState & state, const PosIdx pos, Value * * args, V
static RegisterPrimOp primop_findFile(PrimOp { static RegisterPrimOp primop_findFile(PrimOp {
.name = "__findFile", .name = "__findFile",
.args = {"search path", "lookup path"}, .args = {"search-path", "lookup-path"},
.doc = R"( .doc = R"(
Look up the given path with the given search path. Find *lookup-path* in *search-path*.
A search path is represented list of [attribute sets](./values.md#attribute-set) with two attributes, `prefix`, and `path`. A search path is represented list of [attribute sets](./values.md#attribute-set) with two attributes:
`prefix` is a relative path. - `prefix` is a relative path.
`path` denotes a file system location; the exact syntax depends on the command line interface. - `path` denotes a file system location
The exact syntax depends on the command line interface.
Examples of search path attribute sets: Examples of search path attribute sets:
@ -1722,13 +1723,12 @@ static RegisterPrimOp primop_findFile(PrimOp {
} }
``` ```
The lookup algorithm checks each entry until a match is found, returning a [path value](@docroot@/language/values.html#type-path) of the match. The lookup algorithm checks each entry until a match is found, returning a [path value](@docroot@/language/values.html#type-path) of the match:
This is the process for each entry: - If *lookup-path* matches `prefix`, then the remainder of *lookup-path* (the "suffix") is searched for within the directory denoted by `path`.
If the lookup path matches `prefix`, then the remainder of the lookup path (the "suffix") is searched for within the directory denoted by `patch`.
Note that the `path` may need to be downloaded at this point to look inside. Note that the `path` may need to be downloaded at this point to look inside.
If the suffix is found inside that directory, then the entry is a match; - If the suffix is found inside that directory, then the entry is a match.
the combined absolute path of the directory (now downloaded if need be) and the suffix is returned. The combined absolute path of the directory (now downloaded if need be) and the suffix is returned.
[Lookup path](@docroot@/language/constructs/lookup-path.md) expressions can be [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath): [Lookup path](@docroot@/language/constructs/lookup-path.md) expressions can be [desugared](https://en.wikipedia.org/wiki/Syntactic_sugar) using this and [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath):