fix the way the isProject package flag is set (#1003)

Author: hamishmack

lib/import-and-filter-project.nix

@@ -24,30 +24,43 @@ in project // {
       packages = pkgs.lib.attrsets.mapAttrs (name: value:
         if builtins.isFunction value
           then value
-          else {...}@args:
-            let oldPkg = import value args;
-                packageSrc = if !pkgs.lib.strings.hasPrefix (toString projectNix) (toString oldPkg.src.content)
-                  then toString oldPkg.src.content
-                  else let
-                    subDir = pkgs.lib.strings.removePrefix "/" (
-                      pkgs.lib.strings.removePrefix (toString projectNix)
-                        (toString oldPkg.src.content));
-                    srcRepoPrefix = projectSubDir'' + ".source-repository-packages/";
-                    in if pkgs.lib.strings.hasPrefix srcRepoPrefix subDir
-                      then
-                        pkgs.lib.lists.elemAt sourceRepos (
-                          pkgs.lib.strings.toInt (pkgs.lib.strings.removePrefix srcRepoPrefix subDir))
-                      else haskellLib.appendSubDir {
-                          src = srcRoot;
-                          inherit subDir;
-                          includeSiblings = true; # Filtering sibling dirs of the package dir is done in the
-                                                  # component builder so that relative paths can be used to
-                                                  # reference project directories not in the package subDir.
-                        };
+          else {...}@args: with pkgs.lib.strings;
+            let
+              oldPkg = import value args;
+              # When the package src is in the project dir, this is the subDir it is in.
+              subDir = removePrefix "/" (removePrefix (toString projectNix)
+                                                      (toString oldPkg.src.content));
+              srcRepoPrefix = projectSubDir'' + ".source-repository-packages/";
+
+              packageInfo =
+                if !hasPrefix (toString projectNix) (toString oldPkg.src.content)
+                  then {
+                    # Source location does not match project prefix
+                    isProject = false;
+                    packageSrc = toString oldPkg.src.content;
+                  }
+                else if hasPrefix srcRepoPrefix subDir
+                  then {
+                    # The source is from a source repository
+                    isProject = false;
+                    packageSrc = pkgs.lib.lists.elemAt sourceRepos (
+                      toInt (removePrefix srcRepoPrefix subDir));
+                  }
+                else {
+                    # Source does match project prefix and it is not from a source repository
+                    isProject = true;
+                    packageSrc = haskellLib.appendSubDir {
+                      src = srcRoot;
+                      inherit subDir;
+                      includeSiblings = true; # Filtering sibling dirs of the package dir is done in the
+                                              # component builder so that relative paths can be used to
+                                              # reference project directories not in the package subDir.
+                    };
+                  };
             in oldPkg // {
-              src = (pkgs.lib).mkDefault packageSrc;
+              src = (pkgs.lib).mkDefault packageInfo.packageSrc;
               package = oldPkg.package // {
-                isProject = (pkgs.lib).mkDefault true;
+                isProject = (pkgs.lib).mkDefault packageInfo.isProject;
               };
             }) old;
     };