bundlerEnv: refactor

Add `pname` attribute: if passed, the derivation name defaults to the
gem name + version and only expose the gem's bin.

Add `gemdir` attribute: gives a default lookup path for the Gemfile,
Gemfile.lock and gemset.nix.

Set the `meta.platforms' to `ruby.meta.platforms' by default.

pkgs/development/ruby-modules/bundler-env/default.nix

@@ -6,7 +6,14 @@
 , tree
 }@defs:
 
-{ name, gemset, gemfile, lockfile, ruby ? defs.ruby, gemConfig ? defaultGemConfig
+{ name ? null
+, pname ? null
+, gemdir ? null
+, gemfile ? null
+, lockfile ? null
+, gemset ? null
+, ruby ? defs.ruby
+, gemConfig ? defaultGemConfig
 , postBuild ? null
 , document ? []
 , meta ? {}
@@ -16,54 +23,95 @@
 }@args:
 
 let
-  importedGemset = import gemset;
+  drvName =
+    if name != null then name
+    else if pname != null then "${toString pname}-${mainGem.version}"
+    else throw "bundlerEnv: either pname or name must be set";
+
+  mainGem =
+    if pname == null then null
+    else gems."${pname}" or (throw "bundlerEnv: gem ${pname} not found");
+
+  gemfile' =
+    if gemfile == null then gemdir + "/Gemfile"
+    else gemfile;
+
+  lockfile' =
+    if lockfile == null then gemdir + "/Gemfile.lock"
+    else lockfile;
+
+  gemset' =
+    if gemset == null then gemdir + "/gemset.nix"
+    else gemset;
+
+  importedGemset = import gemset';
+
   filteredGemset = (lib.filterAttrs (name: attrs:
     if (builtins.hasAttr "groups" attrs)
     then (builtins.any (gemGroup: builtins.any (group: group == gemGroup) groups) attrs.groups)
     else true
   ) importedGemset);
+
   applyGemConfigs = attrs:
     (if gemConfig ? "${attrs.gemName}"
     then attrs // gemConfig."${attrs.gemName}" attrs
     else attrs);
+
   configuredGemset = lib.flip lib.mapAttrs filteredGemset (name: attrs:
     applyGemConfigs (attrs // { inherit ruby; gemName = name; })
   );
+
   hasBundler = builtins.hasAttr "bundler" filteredGemset;
-  bundler = if hasBundler then gems.bundler else defs.bundler.override (attrs: { inherit ruby; });
+
+  bundler =
+    if hasBundler then gems.bundler
+    else defs.bundler.override (attrs: { inherit ruby; });
+
   gems = lib.flip lib.mapAttrs configuredGemset (name: attrs:
     buildRubyGem ((removeAttrs attrs ["source"]) // attrs.source // {
       inherit ruby;
       gemName = name;
       gemPath = map (gemName: gems."${gemName}") (attrs.dependencies or []);
     }));
+
   # We have to normalize the Gemfile.lock, otherwise bundler tries to be
   # helpful by doing so at run time, causing executables to immediately bail
   # out. Yes, I'm serious.
   confFiles = runCommand "gemfile-and-lockfile" {} ''
     mkdir -p $out
-    cp ${gemfile} $out/Gemfile
-    cp ${lockfile} $out/Gemfile.lock
+    cp ${gemfile'} $out/Gemfile
+    cp ${lockfile'} $out/Gemfile.lock
   '';
+
   envPaths = lib.attrValues gems ++ lib.optional (!hasBundler) bundler;
+
+  binPaths = if mainGem != null then [ mainGem ] else envPaths;
+
   bundlerEnv = buildEnv {
-    inherit name ignoreCollisions;
+    inherit ignoreCollisions;
+
+    name = drvName;
+
     paths = envPaths;
     pathsToLink = [ "/lib" ];
+
     postBuild = ''
       ${ruby}/bin/ruby ${./gen-bin-stubs.rb} \
         "${ruby}/bin/ruby" \
         "${confFiles}/Gemfile" \
         "$out/${ruby.gemPath}" \
         "${bundler}/${ruby.gemPath}" \
-        ${lib.escapeShellArg envPaths} \
+        ${lib.escapeShellArg binPaths} \
         ${lib.escapeShellArg groups}
     '' + lib.optionalString (postBuild != null) postBuild;
+
+    meta = { platforms = ruby.meta.platforms; } // meta;
+
     passthru = rec {
-      inherit ruby bundler meta gems;
+      inherit ruby bundler gems;
 
       wrappedRuby = stdenv.mkDerivation {
-        name = "wrapped-ruby-${name}";
+        name = "wrapped-ruby-${drvName}";
         nativeBuildInputs = [ makeWrapper ];
         buildCommand = ''
           mkdir -p $out/bin
@@ -87,7 +135,7 @@ let
           require 'bundler/setup'
         '';
         in stdenv.mkDerivation {
-          name = "interactive-${name}-environment";
+          name = "interactive-${drvName}-environment";
           nativeBuildInputs = [ wrappedRuby bundlerEnv ];
           shellHook = ''
             export OLD_IRBRC="$IRBRC"
@@ -102,7 +150,5 @@ let
         };
     };
   };
-
 in
-
-bundlerEnv
+  bundlerEnv