Looking up package revisions in inputMap

builder/default.nix

@@ -1,4 +1,4 @@
-{ pkgs, buildPackages, evalPackages, stdenv, lib, haskellLib, ghc, compiler-nix-name, fetchurl, pkgconfig, nonReinstallablePkgs, hsPkgs, compiler }:
+{ pkgs, buildPackages, evalPackages, stdenv, lib, haskellLib, ghc, compiler-nix-name, fetchurl, pkgconfig, nonReinstallablePkgs, hsPkgs, compiler, inputMap }:
 
 let
   # Builds a single component of a package.
@@ -83,7 +83,7 @@ in {
   # Build a Haskell package from its config.
   # TODO: this pkgs is the adjusted pkgs, but pkgs.pkgs is unadjusted
   build-package = haskellLib.weakCallPackage pkgs ./hspkg-builder.nix {
-    inherit haskellLib ghc compiler-nix-name comp-builder setup-builder;
+    inherit haskellLib ghc compiler-nix-name comp-builder setup-builder inputMap;
   };
 
   inherit shellFor makeConfigFiles;

builder/hspkg-builder.nix

@@ -1,4 +1,4 @@
-{ pkgs, buildPackages, stdenv, lib, haskellLib, ghc, compiler-nix-name, fetchurl, runCommand, comp-builder, setup-builder }:
+{ pkgs, buildPackages, stdenv, lib, haskellLib, ghc, compiler-nix-name, fetchurl, runCommand, comp-builder, setup-builder, inputMap }:
 
 config:
 { flags
@@ -30,12 +30,23 @@ let
       "ghc902/filepath-1.4.2.1" = "/libraries/filepath";
     }."${compiler-nix-name}/${name}" or null;
   src = if bundledSrc == null then pkg.src else ghc.configured-src + bundledSrc;
+  baseUrlMatch = __match "(.*)/package/[^/]*" pkg.src.url;
   cabalFile = if revision == null || revision == 0 || bundledSrc != null then null else
-    fetchurl {
-      name = "${name}-${toString revision}.cabal";
-      url = "https://hackage.haskell.org/package/${name}/revision/${toString revision}.cabal";
-      sha256 = revisionSha256;
-    };
+    if pkgs.lib.hasPrefix "mirror://hackage/" pkg.src.url
+      then fetchurl {
+        name = "${name}-${toString revision}.cabal";
+        url = "https://hackage.haskell.org/package/${name}/revision/${toString revision}.cabal";
+        sha256 = revisionSha256;
+      }
+    else if baseUrlMatch != null
+      then builtins.path {
+        path = inputMap.${__head baseUrlMatch}
+            or (throw "Unable to find inputMap entry for repository '${__head baseUrlMatch}' while looking for '${package.identifier.name}' revision.")
+          + "/index/${package.identifier.name}/${package.identifier.version}/${package.identifier.name}.cabal";
+        sha256 = revisionSha256;
+        recursive = false;
+      }
+    else throw "Unexpected url '${pkg.src.url}' format while looking for '${package.identifier.name}' revision";
 
   defaultSetupSrc = if stdenv.hostPlatform.isGhcjs then ./Setup.ghcjs.hs else ./Setup.hs;
 

modules/component-driver.nix

@@ -4,7 +4,7 @@ let
     inherit haskellLib;
     ghc = config.ghc.package;
     compiler-nix-name = config.compiler.nix-name;
-    inherit (config) nonReinstallablePkgs hsPkgs compiler evalPackages;
+    inherit (config) nonReinstallablePkgs hsPkgs compiler evalPackages inputMap;
   };
 
 in
@@ -89,6 +89,11 @@ in
       __elem config.compiler.nix-name ["ghc901" "ghc902" "ghc921" "ghc922" "ghc923" "ghc924"]) [
       "ghc-bignum" ];
 
+  options.inputMap = lib.mkOption {
+    type = lib.types.attrsOf lib.types.unspecified;
+    default = {};
+  };
+
   options.hsPkgs = lib.mkOption {
     type = lib.types.unspecified;
   };

overlays/haskell.nix

@@ -510,7 +510,7 @@ final: prev: {
         # plan-nix without building the project.
         cabalProject' =
           projectModule: haskellLib.evalProjectModule ../modules/cabal-project.nix projectModule (
-            { src, compiler-nix-name, evalPackages, ... }@args:
+            { src, compiler-nix-name, evalPackages, inputMap, ... }@args:
             let
               callProjectResults = callCabalProjectToNix args;
               plan-pkgs = importAndFilterProject {
@@ -538,6 +538,7 @@ final: prev: {
                     ++ [ {
                       compiler.nix-name = final.lib.mkForce args.compiler-nix-name;
                       evalPackages = final.lib.mkDefault evalPackages;
+                      inputMap = final.lib.mkDefault inputMap;
                     } ];
                   extra-hackages = args.extra-hackages or [] ++ callProjectResults.extra-hackages;
                 };