Merge pull request #247825 from tweag/lib.path-md
Minor `lib.path` documentation consistency improvements
This commit is contained in:
Silvan Mosberger
GitHub
commit
c096e03491
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@ -121,17 +121,18 @@ let
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in /* No rec! Add dependencies on this file at the top. */ {
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/* Append a subpath string to a path.
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/*
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Append a subpath string to a path.
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Like `path + ("/" + string)` but safer, because it errors instead of returning potentially surprising results.
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More specifically, it checks that the first argument is a [path value type](https://nixos.org/manual/nix/stable/language/values.html#type-path"),
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and that the second argument is a valid subpath string (see `lib.path.subpath.isValid`).
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and that the second argument is a [valid subpath string](#function-library-lib.path.subpath.isValid).
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Laws:
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- Not influenced by subpath normalisation
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- Not influenced by subpath [normalisation](#function-library-lib.path.subpath.normalise):
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append p s == append p (subpath.normalise s)
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append p s == append p (subpath.normalise s)
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Type:
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append :: Path -> String -> Path
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@ -175,26 +176,26 @@ in /* No rec! Add dependencies on this file at the top. */ {
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path + ("/" + subpath);
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/*
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Whether the first path is a component-wise prefix of the second path.
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Whether the first path is a component-wise prefix of the second path.
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Laws:
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Laws:
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- `hasPrefix p q` is only true if `q == append p s` for some subpath `s`.
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- `hasPrefix p q` is only true if [`q == append p s`](#function-library-lib.path.append) for some [subpath](#function-library-lib.path.subpath.isValid) `s`.
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- `hasPrefix` is a [non-strict partial order](https://en.wikipedia.org/wiki/Partially_ordered_set#Non-strict_partial_order) over the set of all path values
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- `hasPrefix` is a [non-strict partial order](https://en.wikipedia.org/wiki/Partially_ordered_set#Non-strict_partial_order) over the set of all path values.
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Type:
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hasPrefix :: Path -> Path -> Bool
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Type:
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hasPrefix :: Path -> Path -> Bool
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Example:
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hasPrefix /foo /foo/bar
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=> true
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hasPrefix /foo /foo
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=> true
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hasPrefix /foo/bar /foo
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=> false
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hasPrefix /. /foo
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=> true
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Example:
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hasPrefix /foo /foo/bar
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=> true
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hasPrefix /foo /foo
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=> true
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hasPrefix /foo/bar /foo
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=> false
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hasPrefix /. /foo
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=> true
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*/
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hasPrefix =
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path1:
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@ -219,27 +220,27 @@ in /* No rec! Add dependencies on this file at the top. */ {
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take (length path1Deconstructed.components) path2Deconstructed.components == path1Deconstructed.components;
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/*
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Remove the first path as a component-wise prefix from the second path.
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The result is a normalised subpath string, see `lib.path.subpath.normalise`.
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Remove the first path as a component-wise prefix from the second path.
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The result is a [normalised subpath string](#function-library-lib.path.subpath.normalise).
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Laws:
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Laws:
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- Inverts `append` for normalised subpaths:
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- Inverts [`append`](#function-library-lib.path.append) for [normalised subpath string](#function-library-lib.path.subpath.normalise):
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removePrefix p (append p s) == subpath.normalise s
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removePrefix p (append p s) == subpath.normalise s
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Type:
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removePrefix :: Path -> Path -> String
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Type:
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removePrefix :: Path -> Path -> String
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Example:
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removePrefix /foo /foo/bar/baz
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=> "./bar/baz"
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removePrefix /foo /foo
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=> "./."
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removePrefix /foo/bar /foo
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=> <error>
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removePrefix /. /foo
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=> "./foo"
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Example:
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removePrefix /foo /foo/bar/baz
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=> "./bar/baz"
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removePrefix /foo /foo
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=> "./."
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removePrefix /foo/bar /foo
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=> <error>
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removePrefix /. /foo
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=> "./foo"
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*/
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removePrefix =
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path1:
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@ -272,41 +273,43 @@ in /* No rec! Add dependencies on this file at the top. */ {
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joinRelPath components;
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/*
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Split the filesystem root from a [path](https://nixos.org/manual/nix/stable/language/values.html#type-path).
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The result is an attribute set with these attributes:
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- `root`: The filesystem root of the path, meaning that this directory has no parent directory.
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- `subpath`: The [normalised subpath string](#function-library-lib.path.subpath.normalise) that when [appended](#function-library-lib.path.append) to `root` returns the original path.
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Split the filesystem root from a [path](https://nixos.org/manual/nix/stable/language/values.html#type-path).
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The result is an attribute set with these attributes:
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- `root`: The filesystem root of the path, meaning that this directory has no parent directory.
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- `subpath`: The [normalised subpath string](#function-library-lib.path.subpath.normalise) that when [appended](#function-library-lib.path.append) to `root` returns the original path.
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Laws:
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- [Appending](#function-library-lib.path.append) the `root` and `subpath` gives the original path:
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Laws:
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- [Appending](#function-library-lib.path.append) the `root` and `subpath` gives the original path:
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p ==
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append
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(splitRoot p).root
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(splitRoot p).subpath
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p ==
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append
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(splitRoot p).root
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(splitRoot p).subpath
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- Trying to get the parent directory of `root` using [`readDir`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-readDir) returns `root` itself:
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- Trying to get the parent directory of `root` using [`readDir`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-readDir) returns `root` itself:
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dirOf (splitRoot p).root == (splitRoot p).root
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dirOf (splitRoot p).root == (splitRoot p).root
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Type:
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splitRoot :: Path -> { root :: Path, subpath :: String }
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Type:
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splitRoot :: Path -> { root :: Path, subpath :: String }
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Example:
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splitRoot /foo/bar
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=> { root = /.; subpath = "./foo/bar"; }
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Example:
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splitRoot /foo/bar
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=> { root = /.; subpath = "./foo/bar"; }
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splitRoot /.
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=> { root = /.; subpath = "./."; }
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splitRoot /.
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=> { root = /.; subpath = "./."; }
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# Nix neutralises `..` path components for all path values automatically
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splitRoot /foo/../bar
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=> { root = /.; subpath = "./bar"; }
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# Nix neutralises `..` path components for all path values automatically
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splitRoot /foo/../bar
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=> { root = /.; subpath = "./bar"; }
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splitRoot "/foo/bar"
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=> <error>
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splitRoot "/foo/bar"
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=> <error>
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*/
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splitRoot = path:
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splitRoot =
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# The path to split the root off of
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path:
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assert assertMsg
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(isPath path)
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"lib.path.splitRoot: Argument is of type ${typeOf path}, but a path was expected";
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@ -317,46 +320,47 @@ in /* No rec! Add dependencies on this file at the top. */ {
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subpath = joinRelPath deconstructed.components;
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};
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/* Whether a value is a valid subpath string.
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/*
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Whether a value is a valid subpath string.
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A subpath string points to a specific file or directory within an absolute base directory.
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It is a stricter form of a relative path that excludes `..` components, since those could escape the base directory.
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A subpath string points to a specific file or directory within an absolute base directory.
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It is a stricter form of a relative path that excludes `..` components, since those could escape the base directory.
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- The value is a string
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- The value is a string.
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- The string is not empty
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- The string is not empty.
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- The string doesn't start with a `/`
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- The string doesn't start with a `/`.
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- The string doesn't contain any `..` path components
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- The string doesn't contain any `..` path components.
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Type:
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subpath.isValid :: String -> Bool
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Type:
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subpath.isValid :: String -> Bool
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Example:
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# Not a string
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subpath.isValid null
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=> false
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Example:
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# Not a string
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subpath.isValid null
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=> false
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# Empty string
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subpath.isValid ""
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=> false
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# Empty string
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subpath.isValid ""
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=> false
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# Absolute path
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subpath.isValid "/foo"
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=> false
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# Absolute path
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subpath.isValid "/foo"
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=> false
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# Contains a `..` path component
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subpath.isValid "../foo"
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=> false
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# Contains a `..` path component
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subpath.isValid "../foo"
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=> false
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# Valid subpath
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subpath.isValid "foo/bar"
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=> true
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# Valid subpath
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subpath.isValid "foo/bar"
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=> true
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# Doesn't need to be normalised
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subpath.isValid "./foo//bar/"
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=> true
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# Doesn't need to be normalised
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subpath.isValid "./foo//bar/"
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=> true
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*/
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subpath.isValid =
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# The value to check
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@ -364,15 +368,16 @@ in /* No rec! Add dependencies on this file at the top. */ {
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subpathInvalidReason value == null;
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/* Join subpath strings together using `/`, returning a normalised subpath string.
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/*
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Join subpath strings together using `/`, returning a normalised subpath string.
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Like `concatStringsSep "/"` but safer, specifically:
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- All elements must be valid subpath strings, see `lib.path.subpath.isValid`
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- All elements must be [valid subpath strings](#function-library-lib.path.subpath.isValid).
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- The result gets normalised, see `lib.path.subpath.normalise`
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- The result gets [normalised](#function-library-lib.path.subpath.normalise).
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- The edge case of an empty list gets properly handled by returning the neutral subpath `"./."`
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- The edge case of an empty list gets properly handled by returning the neutral subpath `"./."`.
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Laws:
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@ -386,12 +391,12 @@ in /* No rec! Add dependencies on this file at the top. */ {
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subpath.join [ (subpath.normalise p) "./." ] == subpath.normalise p
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subpath.join [ "./." (subpath.normalise p) ] == subpath.normalise p
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- Normalisation - the result is normalised according to `lib.path.subpath.normalise`:
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- Normalisation - the result is [normalised](#function-library-lib.path.subpath.normalise):
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subpath.join ps == subpath.normalise (subpath.join ps)
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- For non-empty lists, the implementation is equivalent to normalising the result of `concatStringsSep "/"`.
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Note that the above laws can be derived from this one.
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- For non-empty lists, the implementation is equivalent to [normalising](#function-library-lib.path.subpath.normalise) the result of `concatStringsSep "/"`.
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Note that the above laws can be derived from this one:
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ps != [] -> subpath.join ps == subpath.normalise (concatStringsSep "/" ps)
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@ -439,108 +444,109 @@ in /* No rec! Add dependencies on this file at the top. */ {
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) 0 subpaths;
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/*
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Split [a subpath](#function-library-lib.path.subpath.isValid) into its path component strings.
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Throw an error if the subpath isn't valid.
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Note that the returned path components are also valid subpath strings, though they are intentionally not [normalised](#function-library-lib.path.subpath.normalise).
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Split [a subpath](#function-library-lib.path.subpath.isValid) into its path component strings.
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Throw an error if the subpath isn't valid.
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Note that the returned path components are also [valid subpath strings](#function-library-lib.path.subpath.isValid), though they are intentionally not [normalised](#function-library-lib.path.subpath.normalise).
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Laws:
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Laws:
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- Splitting a subpath into components and [joining](#function-library-lib.path.subpath.join) the components gives the same subpath but [normalised](#function-library-lib.path.subpath.normalise):
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- Splitting a subpath into components and [joining](#function-library-lib.path.subpath.join) the components gives the same subpath but [normalised](#function-library-lib.path.subpath.normalise):
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subpath.join (subpath.components s) == subpath.normalise s
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subpath.join (subpath.components s) == subpath.normalise s
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Type:
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subpath.components :: String -> [ String ]
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Type:
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subpath.components :: String -> [ String ]
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Example:
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subpath.components "."
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=> [ ]
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Example:
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subpath.components "."
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=> [ ]
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subpath.components "./foo//bar/./baz/"
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=> [ "foo" "bar" "baz" ]
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subpath.components "./foo//bar/./baz/"
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=> [ "foo" "bar" "baz" ]
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subpath.components "/foo"
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=> <error>
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subpath.components "/foo"
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=> <error>
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*/
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subpath.components =
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# The subpath string to split into components
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subpath:
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assert assertMsg (isValid subpath) ''
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lib.path.subpath.components: Argument is not a valid subpath string:
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${subpathInvalidReason subpath}'';
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splitRelPath subpath;
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/* Normalise a subpath. Throw an error if the subpath isn't valid, see
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`lib.path.subpath.isValid`
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/*
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Normalise a subpath. Throw an error if the subpath isn't [valid](#function-library-lib.path.subpath.isValid).
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- Limit repeating `/` to a single one
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- Limit repeating `/` to a single one.
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- Remove redundant `.` components
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- Remove redundant `.` components.
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- Remove trailing `/` and `/.`
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- Remove trailing `/` and `/.`.
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- Add leading `./`
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- Add leading `./`.
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Laws:
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Laws:
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- Idempotency - normalising multiple times gives the same result:
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- Idempotency - normalising multiple times gives the same result:
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subpath.normalise (subpath.normalise p) == subpath.normalise p
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subpath.normalise (subpath.normalise p) == subpath.normalise p
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- Uniqueness - there's only a single normalisation for the paths that lead to the same file system node:
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- Uniqueness - there's only a single normalisation for the paths that lead to the same file system node:
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subpath.normalise p != subpath.normalise q -> $(realpath ${p}) != $(realpath ${q})
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subpath.normalise p != subpath.normalise q -> $(realpath ${p}) != $(realpath ${q})
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- Don't change the result when appended to a Nix path value:
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- Don't change the result when [appended](#function-library-lib.path.append) to a Nix path value:
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base + ("/" + p) == base + ("/" + subpath.normalise p)
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append base p == append base (subpath.normalise p)
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- Don't change the path according to `realpath`:
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- Don't change the path according to `realpath`:
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$(realpath ${p}) == $(realpath ${subpath.normalise p})
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$(realpath ${p}) == $(realpath ${subpath.normalise p})
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- Only error on invalid subpaths:
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- Only error on [invalid subpaths](#function-library-lib.path.subpath.isValid):
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builtins.tryEval (subpath.normalise p)).success == subpath.isValid p
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builtins.tryEval (subpath.normalise p)).success == subpath.isValid p
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Type:
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subpath.normalise :: String -> String
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Type:
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subpath.normalise :: String -> String
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Example:
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# limit repeating `/` to a single one
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subpath.normalise "foo//bar"
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=> "./foo/bar"
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Example:
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# limit repeating `/` to a single one
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subpath.normalise "foo//bar"
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=> "./foo/bar"
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# remove redundant `.` components
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subpath.normalise "foo/./bar"
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=> "./foo/bar"
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# remove redundant `.` components
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subpath.normalise "foo/./bar"
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=> "./foo/bar"
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# add leading `./`
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subpath.normalise "foo/bar"
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=> "./foo/bar"
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# add leading `./`
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subpath.normalise "foo/bar"
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=> "./foo/bar"
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# remove trailing `/`
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subpath.normalise "foo/bar/"
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=> "./foo/bar"
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# remove trailing `/`
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subpath.normalise "foo/bar/"
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=> "./foo/bar"
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# remove trailing `/.`
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subpath.normalise "foo/bar/."
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=> "./foo/bar"
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# remove trailing `/.`
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subpath.normalise "foo/bar/."
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=> "./foo/bar"
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# Return the current directory as `./.`
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subpath.normalise "."
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=> "./."
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# Return the current directory as `./.`
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subpath.normalise "."
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=> "./."
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# error on `..` path components
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subpath.normalise "foo/../bar"
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=> <error>
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# error on `..` path components
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subpath.normalise "foo/../bar"
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=> <error>
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# error on empty string
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subpath.normalise ""
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=> <error>
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# error on empty string
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subpath.normalise ""
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=> <error>
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# error on absolute path
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subpath.normalise "/foo"
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=> <error>
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# error on absolute path
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subpath.normalise "/foo"
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=> <error>
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*/
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subpath.normalise =
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# The subpath string to normalise
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