Add loadCabalPlan function

Author: hamishmack

lib/load-cabal-plan.nix

@@ -0,0 +1,160 @@
+{haskellLib, pkgs}:
+{callProjectResults, selectedCompiler}:
+let
+  # Read the plan.json file `plan-nix` derivation
+  plan-json = builtins.fromJSON (
+    builtins.unsafeDiscardStringContext (
+      builtins.readFile (callProjectResults.projectNix + "/plan.json")));
+  # All the units in the plan indexed by unit ID.
+  by-id = pkgs.lib.listToAttrs (map (x: { name = x.id; value = x; }) plan-json.install-plan);
+  # Find the names of all the pre-existing packages used by a list of dependencies
+  # (includes transitive dependencies)
+  lookupPreExisting = depends:
+    pkgs.lib.concatMap (d: builtins.attrNames pre-existing-depends.${d}) depends;
+  pre-existing-depends =
+    pkgs.lib.listToAttrs (map (p: {
+      name = p.id;
+      value = pkgs.lib.optionalAttrs (p.type == "pre-existing") { ${p.pkg-name} = null; } //
+        pkgs.lib.listToAttrs (
+          map (dname: { name = dname; value = null; }) (lookupPreExisting (p.depends or p.components.lib.depends)));
+    }) plan-json.install-plan);
+  # Lookup a dependency in `hsPkgs`
+  lookupDependency = hsPkgs: d:
+    pkgs.lib.optional (by-id.${d}.type != "pre-existing") (
+        if by-id.${d}.component-name or "lib" == "lib"
+          then hsPkgs.${d} or hsPkgs.${by-id.${d}.pkg-name}
+          else hsPkgs.${d}.components.sublibs.${pkgs.lib.removePrefix "lib:" by-id.${d}.component-name});
+  # Lookup an executable dependency in `hsPkgs.pkgsBuildBuild`
+  lookupExeDependency = hsPkgs: d:
+    # Try to lookup by ID, but if that fails use the name (currently a different plan is used by pkgsBuildBuild when cross compiling)
+    (hsPkgs.pkgsBuildBuild.${d} or hsPkgs.pkgsBuildBuild.${by-id.${d}.pkg-name}).components.exes.${pkgs.lib.removePrefix "exe:" by-id.${d}.component-name};
+  # Populate `depends`, `pre-existing` and `build-tools`
+  lookupDependencies = hsPkgs: depends: exe-depends: {
+    depends = pkgs.lib.concatMap (lookupDependency hsPkgs) depends;
+    pre-existing = lookupPreExisting depends;
+    build-tools = map (lookupExeDependency hsPkgs) exe-depends;
+  };
+  # Calculate the packages for a component
+  getComponents = cabal2nixComponents: hsPkgs: p:
+    let
+      components = p.components or { ${p.component-name or "lib"} = { inherit (p) depends; exe-depends = p.exe-depends or []; }; };
+      # Other than the `lib` and `setup` components, component names
+      # have a prefix based on their type.
+      componentsWithPrefix = collectionName: prefix:
+        pkgs.lib.listToAttrs (pkgs.lib.concatLists (pkgs.lib.mapAttrsToList (n: c:
+          pkgs.lib.optional (pkgs.lib.hasPrefix "${prefix}:" n) (
+            let
+              name = pkgs.lib.removePrefix "${prefix}:" n;
+              value = (if cabal2nixComponents == null then {} else cabal2nixComponents.${collectionName}.${name}) // {
+                buildable = true;
+              } // lookupDependencies hsPkgs c.depends c.exe-depends;
+            in { inherit name value; }
+          )) components));
+    in
+      pkgs.lib.mapAttrs componentsWithPrefix haskellLib.componentPrefix
+      // pkgs.lib.optionalAttrs (components ? lib) {
+        library = (if cabal2nixComponents == null then {} else cabal2nixComponents.library) // {
+          buildable = true;
+        } // lookupDependencies hsPkgs components.lib.depends components.lib.exe-depends;
+      } // pkgs.lib.optionalAttrs (components ? setup) {
+        setup = {
+          buildable = true;
+        } // lookupDependencies hsPkgs.pkgsBuildBuild (components.setup.depends or []) (components.setup.exe-depends or []);
+      };
+  nixFilesDir = callProjectResults.projectNix + callProjectResults.src.origSubDir or "";
+in {
+  # This replaces the `plan-nix/default.nix`
+  pkgs = (hackage: {
+    packages = pkgs.lib.listToAttrs (
+      # Include entries for the `pre-existing` packages, but leave them as `null`
+      pkgs.lib.concatMap (p:
+        pkgs.lib.optional (p.type == "pre-existing") {
+          name = p.id;
+          value.revision = null;
+        }) plan-json.install-plan
+      # The other packages that are not part of the project itself.
+      ++ pkgs.lib.concatMap (p:
+        pkgs.lib.optional (p.type == "configured" && (p.style == "global" || p.style == "inplace") ) {
+          name = p.id;
+          value.revision =
+            {hsPkgs, ...}@args:
+              let
+                # Read the output of `Cabal2Nix.hs`.  We need it for information not
+                # in the `plan.json` file.
+                cabal2nix = (
+                  if builtins.pathExists (nixFilesDir + "/cabal-files/${p.pkg-name}.nix")
+                    then import (nixFilesDir + "/cabal-files/${p.pkg-name}.nix")
+                  else if builtins.pathExists (nixFilesDir + "/.plan.nix/${p.pkg-name}.nix")
+                    then import (nixFilesDir + "/.plan.nix/${p.pkg-name}.nix")
+                  else (((hackage.${p.pkg-name}).${p.pkg-version}).revisions).default) (args // { hsPkgs = {}; });
+              in pkgs.lib.optionalAttrs (p ? pkg-src-sha256) {
+                sha256 = p.pkg-src-sha256;
+              } // pkgs.lib.optionalAttrs (p.pkg-src.type or "" == "source-repo") {
+                # Replace the source repository packages with versions created when
+                # parsing the `cabal.project` file.
+                src = pkgs.lib.lists.elemAt callProjectResults.sourceRepos (pkgs.lib.strings.toInt p.pkg-src.source-repo.location) + "/${p.pkg-src.source-repo.subdir}";
+              } // pkgs.lib.optionalAttrs (cabal2nix ? package-description-override && p.pkg-version == cabal2nix.package.identifier.version) {
+                # Use the `.cabal` file from the `Cabal2Nix` if it for the matching
+                # version of the package (the one in the plan).
+                inherit (cabal2nix) package-description-override;
+              } // {
+                flags = p.flags; # Use the flags from `plan.json`
+                components = getComponents cabal2nix.components hsPkgs p;
+                package = cabal2nix.package // {
+                  identifier = { name = p.pkg-name; version = p.pkg-version; id = p.id; };
+                  isProject = false;
+                  setup-depends = []; # The correct setup depends will be in `components.setup.depends`
+                };
+              };
+        }) plan-json.install-plan);
+    compiler = {
+      inherit (selectedCompiler) version;
+    };
+  });
+  # Packages in the project (those that are both configure and local)
+  extras = (_hackage: {
+    packages = pkgs.lib.listToAttrs (
+      pkgs.lib.concatMap (p:
+        pkgs.lib.optional (p.type == "configured" && p.style == "local") {
+          name = p.id;
+          value =
+            {hsPkgs, ...}@args:
+              let cabal2nix = import (nixFilesDir + "/.plan.nix/${p.pkg-name}.nix") (args // { hsPkgs = {}; });
+              in pkgs.lib.optionalAttrs (p ? pkg-src-sha256) {
+                sha256 = p.pkg-src-sha256;
+              } // pkgs.lib.optionalAttrs (p.pkg-src.type or "" == "local" && cabal2nix ? cabal-generator) {
+                inherit (cabal2nix) cabal-generator;
+              } // pkgs.lib.optionalAttrs (p.pkg-src.type or "" == "local") {
+                # Find the `src` location based on `p.pkg-src.path`
+                src = if pkgs.lib.hasPrefix "/" p.pkg-src.path
+                  then p.pkg-src.path # Absolute path
+                  else haskellLib.appendSubDir {
+                    # Relative to the project path
+                    inherit (callProjectResults) src;
+                    subDir = pkgs.lib.removePrefix "./" (pkgs.lib.removePrefix "/" (pkgs.lib.removeSuffix "/." (pkgs.lib.removeSuffix "/." (
+                      if pkgs.lib.hasPrefix ".${callProjectResults.src.origSubDir or ""}/" (p.pkg-src.path + "/")
+                        then pkgs.lib.removePrefix ".${callProjectResults.src.origSubDir or ""}" p.pkg-src.path
+                        else throw "Unexpected path ${p.pkg-src.path} expected it to start with .${callProjectResults.src.origSubDir or ""}"))));
+                    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.
+                  };
+              } // {
+                flags = p.flags; # Use the flags from `plan.json`
+                components = getComponents cabal2nix.components hsPkgs p;
+                package = cabal2nix.package // {
+                  identifier = { name = p.pkg-name; version = p.pkg-version; id = p.id; };
+                  isProject = true;
+                  setup-depends = []; # The correct setup depends will be in `components.setup.depends`
+                };
+              };
+        }) plan-json.install-plan);
+  });
+  modules = [
+    { inherit plan-json; }
+    (import ../modules/install-plan/non-reinstallable.nix)
+    (import ../modules/install-plan/override-package-by-name.nix)
+    (import ../modules/install-plan/planned.nix { inherit getComponents; })
+    (import ../modules/install-plan/redirect.nix)
+  ];
+}