nix: Add methods to support develop installations from config.

shell.nix

@@ -1,70 +1,103 b''
 { pkgs ? (import <nixpkgs> {})
 , vcsserverPath ? "./../rhodecode-vcsserver"
 , vcsserverNix ? "shell.nix"
 , doCheck ? true
 }:
 
 let
 
   # Convert vcsserverPath to absolute path.
   vcsserverAbsPath =
     if pkgs.lib.strings.hasPrefix "/" vcsserverPath then
       builtins.toPath "${vcsserverPath}"
     else
       builtins.toPath ("${builtins.getEnv "PWD"}/${vcsserverPath}");
 
   # Import vcsserver if nix file exists, otherwise set it to null.
   vcsserver =
     let
       nixFile = "${vcsserverAbsPath}/${vcsserverNix}";
     in
       if pkgs.lib.pathExists "${nixFile}" then
         builtins.trace
           "Using local vcsserver from ${nixFile}"
           import "${nixFile}" {inherit pkgs;}
       else
           null;
 
   hasVcsserver = !isNull vcsserver;
 
   enterprise-ce = import ./default.nix {
     inherit pkgs doCheck;
   };
 
   ce-pythonPackages = enterprise-ce.pythonPackages;
 
+  # This method looks up a path from `pkgs.config.rc.sources` and returns a
+  # shell script which does a `python setup.py develop` installation of it. If
+  # no path is found it will return an empty string.
+  optionalDevelopInstall = attributeName:
+    let
+      path = pkgs.lib.attrByPath [attributeName] null sources;
+      doIt = doDevelopInstall && path != null;
+    in
+      pkgs.lib.optionalString doIt (
+      builtins.trace "Develop install of ${attributeName} from ${path}" ''
+        echo "Develop install of '${attributeName}' from '${path}' [BEGIN]"
+        pushd ${path}
+        python setup.py develop --prefix $tmp_path --allow-hosts ""
+        popd
+        echo "Develop install of '${attributeName}' from '${path}' [DONE]"
+      '');
+
+  # This method looks up a path from `pkgs.config.rc.sources` and imports the
+  # default.nix file if it exists. It returns the list of build inputs. If no
+  # path is found it will return an empty list.
+  optionalDevelopInstallBuildInputs = attributeName:
+    let
+      path = pkgs.lib.attrByPath [attributeName] null sources;
+      nixFile = "${path}/default.nix";
+      doIt = doDevelopInstall && path != null && pkgs.lib.pathExists "${nixFile}";
+      derivate = import "${nixFile}" {
+        inherit doCheck pkgs pythonPackages;
+      };
+    in
+      pkgs.lib.lists.optionals doIt derivate.propagatedNativeBuildInputs;
+
+  developInstalls = [ "rhodecode-vcsserver" ];
+
 in enterprise-ce.override (attrs: {
   # Avoid that we dump any sources into the store when entering the shell and
   # make development a little bit more convenient.
   src = null;
 
   buildInputs =
     attrs.buildInputs ++
     pkgs.lib.optionals (hasVcsserver) vcsserver.propagatedNativeBuildInputs ++
     (with ce-pythonPackages; [
       bumpversion
       invoke
       ipdb
     ]);
 
   # Somewhat snappier setup of the development environment
   # TODO: think of supporting a stable path again, so that multiple shells
   #       can share it.
   postShellHook = ''
     # Custom prompt to distinguish from other dev envs.
     export PS1="\n\[\033[1;32m\][CE-shell:\w]$\[\033[0m\] "
 
     tmp_path=$(mktemp -d)
     export PATH="$tmp_path/bin:$PATH"
     export PYTHONPATH="$tmp_path/${ce-pythonPackages.python.sitePackages}:$PYTHONPATH"
     mkdir -p $tmp_path/${ce-pythonPackages.python.sitePackages}
     python setup.py develop --prefix $tmp_path --allow-hosts ""
     '' + enterprise-ce.linkNodeAndBowerPackages +
     pkgs.lib.strings.optionalString (hasVcsserver) ''
       # Setup the vcsserver development egg.
       pushd ${vcsserverAbsPath}
       python setup.py develop --prefix $tmp_path --allow-hosts ""
       popd
     '';
 
 })