wrapFish: add fish shell wrapper package

doc/builders/packages/fish.section.md

@@ -0,0 +1,50 @@
+# Fish {#sec-fish}
+
+Fish is a "smart and user-friendly command line shell" with support for plugins.
+
+
+## Vendor Fish scripts {#sec-fish-vendor}
+
+Any package may ship its own Fish completions, configuration snippets, and
+functions. Those should be installed to
+`$out/share/fish/vendor_{completions,conf,functions}.d` respectively.
+
+When the `programs.fish.enable` and
+`programs.fish.vendor.{completions,config,functions}.enable` options from the
+NixOS Fish module are set to true, those paths are symlinked in the current
+system environment and automatically loaded by Fish.
+
+
+## Packaging Fish plugins {#sec-fish-plugins-pkg}
+
+While packages providing standalone executables belong to the top level,
+packages which have the sole purpose of extending Fish belong to the
+`fishPlugins` scope and should be registered in
+`pkgs/shells/fish/plugins/default.nix`.
+
+The `buildFishPlugin` utility function can be used to automatically copy Fish
+scripts from `$src/{completions,conf,conf.d,functions}` to the standard vendor
+installation paths. It also sets up the test environment so that the optional
+`checkPhase` is executed in a Fish shell with other already packaged plugins
+and package-local Fish functions specified in `checkPlugins` and
+`checkFunctionDirs` respectively.
+
+See `pkgs/shells/fish/plugins/pure.nix` for an example of Fish plugin package
+using `buildFishPlugin` and running unit tests with the `fishtape` test runner.
+
+
+## Fish wrapper {#sec-fish-wrapper}
+
+The `wrapFish` package is a wrapper around Fish which can be used to create
+Fish shells initialised with some plugins as well as completions, configuration
+snippets and functions sourced from the given paths. This provides a convenient
+way to test Fish plugins and scripts without having to alter the environment.
+
+```nix
+wrapFish {
+  pluginPkgs = with fishPlugins; [ pure foreign-env ];
+  completionDirs = [];
+  functionDirs = [];
+  confDirs = [ "/path/to/some/fish/init/dir/" ];
+}
+```

doc/builders/packages/index.xml

@@ -11,6 +11,7 @@
  <xi:include href="elm.xml" />
  <xi:include href="emacs.section.xml" />
  <xi:include href="firefox.section.xml" />
+ <xi:include href="fish.section.xml" />
  <xi:include href="ibus.xml" />
  <xi:include href="kakoune.section.xml" />
  <xi:include href="linux.section.xml" />

pkgs/shells/fish/plugins/build-fish-plugin.nix

@@ -1,23 +1,6 @@
-{ stdenv, lib, writeShellScriptBin, writeScript, fish }:
+{ stdenv, lib, writeScript, wrapFish }:
 
-let
-  rtpPath = "share/fish";
-
-  mapToFuncPath = v:
-    if lib.isString v
-    then v
-    else "${v}/${rtpPath}/vendor_functions.d";
-
-  fishWithFunctionPath = plugins: let
-    funcPaths = map mapToFuncPath plugins;
-  in writeShellScriptBin "fish" ''
-    ${fish}/bin/fish \
-      --init-command \
-        "set --prepend fish_function_path ${lib.escapeShellArgs funcPaths}" \
-      "$@"
-  '';
-
-in attrs@{
+attrs@{
   pname,
   version,
   src,
@@ -32,8 +15,10 @@ in attrs@{
   installPath ? lib.getName pname,
 
   checkInputs ? [],
-  # plugins or paths to add to the function path of the test fish shell
-  checkFunctionPath ? [],
+  # plugin packages to add to the vendor paths of the test fish shell
+  checkPlugins ? [],
+  # vendor directories to add to the function path of the test fish shell
+  checkFunctionDirs ? [],
   # test script to be executed in a fish shell
   checkPhase ? "",
   doCheck ? checkPhase != "",
@@ -52,7 +37,7 @@ stdenv.mkDerivation (attrs // {
     (
       install_vendor_files() {
         source="$1"
-        target="$out/${rtpPath}/vendor_$2.d"
+        target="$out/share/fish/vendor_$2.d"
 
         [ -d $source ] || return 0
         mkdir -p $target
@@ -69,7 +54,12 @@ stdenv.mkDerivation (attrs // {
   '';
 
   inherit doCheck;
-  checkInputs = [ (fishWithFunctionPath checkFunctionPath) ] ++ checkInputs;
+
+  checkInputs = [ (wrapFish {
+    pluginPkgs = checkPlugins;
+    functionDirs = checkFunctionDirs;
+  }) ] ++ checkInputs;
+
   checkPhase = ''
     export HOME=$(mktemp -d)  # fish wants a writable home
     fish "${writeScript "${name}-test" checkPhase}"

pkgs/shells/fish/plugins/fishtape.nix

@@ -11,7 +11,7 @@ buildFishPlugin rec {
     sha256 = "0dxcyhs2shhgy5xnwcimqja8vqsyk841x486lgq13i3y1h0kp2kd";
   };
 
-  checkFunctionPath = [ "./" ]; # fishtape is introspective
+  checkFunctionDirs = [ "./" ]; # fishtape is introspective
   checkPhase = ''
     rm test/tty.fish  # test expects a tty
     fishtape test/*.fish

pkgs/shells/fish/plugins/pure.nix

@@ -12,7 +12,7 @@ buildFishPlugin rec {
   };
 
   checkInputs = [ git ];
-  checkFunctionPath = [ fishtape ];
+  checkPlugins = [ fishtape ];
   checkPhase = ''
     # https://github.com/rafaelrinaldi/pure/issues/264
     rm tests/_pure_string_width.test.fish

pkgs/shells/fish/wrapper.nix

@@ -0,0 +1,25 @@
+{ lib, writeShellScriptBin, fish }:
+
+with lib;
+
+makeOverridable ({
+  completionDirs ? [],
+  functionDirs ? [],
+  confDirs ? [],
+  pluginPkgs ? []
+}:
+
+let
+  vendorDir = kind: plugin: "${plugin}/share/fish/vendor_${kind}.d";
+  complPath = completionDirs ++ map (vendorDir "completions") pluginPkgs;
+  funcPath = functionDirs ++ map (vendorDir "functions") pluginPkgs;
+  confPath = confDirs ++ map (vendorDir "conf") pluginPkgs;
+  safeConfPath = map escapeShellArg confPath;
+
+in writeShellScriptBin "fish" ''
+  ${fish}/bin/fish --init-command "
+    set --prepend fish_complete_path ${escapeShellArgs complPath}
+    set --prepend fish_function_path ${escapeShellArgs funcPath}
+    for c in {${concatStringsSep "," safeConfPath}}/*; source $c; end
+  " "$@"
+'')

pkgs/top-level/all-packages.nix

@@ -8843,6 +8843,8 @@ in
 
   fish = callPackage ../shells/fish { };
 
+  wrapFish = callPackage ../shells/fish/wrapper.nix { };
+
   fishPlugins = recurseIntoAttrs (callPackage ../shells/fish/plugins { });
 
   ion = callPackage ../shells/ion {