Merge pull request #723 from emilazy/rationalize-nixpkgs-handling

Rationalize handling of Nixpkgs

2 files changed, 45 insertions, 59 deletions

diff --git a/modules/system/flake-overrides.nix b/modules/system/flake-overrides.nix
deleted file mode 100644
index df3eb16..0000000
--- a/modules/system/flake-overrides.nix
+++ /dev/null
@@ -1,20 +0,0 @@
-{ lib, inputs, ... }:
-
-with lib;
-
-let
-  inherit (inputs) darwin nixpkgs;
-in
-
-{
-  config = {
-    system.checks.verifyNixPath = mkDefault false;
-    system.checks.verifyNixChannels = mkDefault false;
-
-    system.darwinVersionSuffix = ".${darwin.shortRev or "dirty"}";
-    system.darwinRevision = mkIf (darwin ? rev) darwin.rev;
-
-    system.nixpkgsVersionSuffix = ".${substring 0 8 (nixpkgs.lastModifiedDate or nixpkgs.lastModified or "19700101")}.${nixpkgs.shortRev or "dirty"}";
-    system.nixpkgsRevision = mkIf (nixpkgs ? rev) nixpkgs.rev;
-  };
-}
diff --git a/modules/system/version.nix b/modules/system/version.nix
index 6801918..e45f667 100644
--- a/modules/system/version.nix
+++ b/modules/system/version.nix
@@ -1,4 +1,4 @@
-{ options, config, lib, pkgs, ... }:
+{ options, config, lib, ... }:
 
 with lib;
 
@@ -7,27 +7,28 @@ let
 
   defaultStateVersion = options.system.stateVersion.default;
 
-  parseGit = path:
-    if pathExists "${path}/.git" then rec {
-      rev = commitIdFromGitRepo "${path}/.git";
-      shortRev = substring 0 7 rev;
-    }
-    else if pathExists "${path}/.git-revision" then rec {
-      rev = fileContents "${path}/.git-revision";
-      shortRev = substring 0 7 rev;
-    }
-    else {
-      shortRev = "0000000";
-    };
-
-  darwin = parseGit (toString ../..);
-  nixpkgs = parseGit (toString pkgs.path);
-
-  releaseFile = "${toString pkgs.path}/.version";
-  suffixFile = "${toString pkgs.path}/.version-suffix";
-
-  nixpkgsSuffix = if pathExists suffixFile then fileContents suffixFile
-                  else ".git." + nixpkgs.shortRev;
+  # Based on `lib.trivial.revisionWithDefault` from nixpkgs.
+  gitRevision = path:
+    if pathIsGitRepo "${path}/.git"
+    then commitIdFromGitRepo "${path}/.git"
+    else if pathExists "${path}/.git-revision"
+    then fileContents "${path}/.git-revision"
+    else null;
+
+  nixpkgsSrc = config.nixpkgs.source;
+
+  # If `nixpkgs.constructedByUs` is true, then Nixpkgs was imported from
+  # `nixpkgs.source` and we can use revision information (flake input,
+  # `builtins.fetchGit`, etc.) from it. Otherwise `pkgs` could be
+  # anything and we can't reliably determine exact version information,
+  # but if the configuration explicitly sets `nixpkgs.source` we
+  # trust it.
+  useSourceRevision =
+    (config.nixpkgs.constructedByUs
+      || options.nixpkgs.source.highestPrio < (lib.mkDefault {}).priority)
+    && isAttrs nixpkgsSrc
+    && (nixpkgsSrc._type or null == "flake"
+      || isString (nixpkgsSrc.rev or null));
 in
 
 {
@@ -56,62 +57,67 @@ in
     system.darwinVersion = mkOption {
       internal = true;
       type = types.str;
-      description = lib.mdDoc "The full darwin version (e.g. `darwin4.master`).";
+      default = "darwin${toString cfg.stateVersion}${cfg.darwinVersionSuffix}";
+      description = lib.mdDoc "The full darwin version (e.g. `darwin4.2abdb5a`).";
     };
 
     system.darwinVersionSuffix = mkOption {
       internal = true;
       type = types.str;
+      default = if cfg.darwinRevision != null
+        then ".${substring 0 7 cfg.darwinRevision}"
+        else "";
       description = lib.mdDoc "The short darwin version suffix (e.g. `.2abdb5a`).";
     };
 
     system.darwinRevision = mkOption {
       internal = true;
-      type = types.str;
-      default = "master";
+      type = types.nullOr types.str;
+      default = gitRevision (toString ../..);
       description = lib.mdDoc "The darwin git revision from which this configuration was built.";
     };
 
     system.nixpkgsRelease = mkOption {
       readOnly = true;
       type = types.str;
+      default = lib.trivial.release;
       description = lib.mdDoc "The nixpkgs release (e.g. `16.03`).";
     };
 
     system.nixpkgsVersion = mkOption {
       internal = true;
       type = types.str;
+      default = cfg.nixpkgsRelease + cfg.nixpkgsVersionSuffix;
       description = lib.mdDoc "The full nixpkgs version (e.g. `16.03.1160.f2d4ee1`).";
     };
 
     system.nixpkgsVersionSuffix = mkOption {
       internal = true;
       type = types.str;
+      default = if useSourceRevision
+        then ".${lib.substring 0 8 (nixpkgsSrc.lastModifiedDate or nixpkgsSrc.lastModified or "19700101")}.${nixpkgsSrc.shortRev or "dirty"}"
+        else lib.trivial.versionSuffix;
       description = lib.mdDoc "The short nixpkgs version suffix (e.g. `.1160.f2d4ee1`).";
     };
 
     system.nixpkgsRevision = mkOption {
       internal = true;
-      type = types.str;
+      type = types.nullOr types.str;
+      default = if useSourceRevision && nixpkgsSrc ? rev
+        then nixpkgsSrc.rev
+        else lib.trivial.revisionWithDefault null;
       description = lib.mdDoc "The nixpkgs git revision from which this configuration was built.";
     };
   };
 
   config = {
-
-    # These defaults are set here rather than up there so that
-    # changing them would not rebuild the manual
+    # This default is set here rather than up there so that the options
+    # documentation is not reprocessed on every commit
     system.darwinLabel = mkDefault "${cfg.nixpkgsVersion}+${cfg.darwinVersion}";
-    system.darwinVersion = mkDefault "darwin${toString cfg.stateVersion}${cfg.darwinVersionSuffix}";
-    system.darwinVersionSuffix = mkDefault ".${darwin.shortRev}";
-    system.darwinRevision = mkIf (darwin ? rev) (mkDefault darwin.rev);
-
-    system.nixpkgsVersion = mkDefault "${cfg.nixpkgsRelease}${cfg.nixpkgsVersionSuffix}";
-    system.nixpkgsRelease = mkDefault (fileContents releaseFile);
-    system.nixpkgsVersionSuffix = mkDefault nixpkgsSuffix;
-    system.nixpkgsRevision = mkIf (nixpkgs ? rev) (mkDefault nixpkgs.rev);
-
-    assertions = [ { assertion = cfg.stateVersion <= defaultStateVersion; message = "system.stateVersion = ${toString cfg.stateVersion}; is not a valid value"; } ];
 
+    assertions = [ {
+      assertion = cfg.stateVersion <= defaultStateVersion;
+      message = "system.stateVersion = ${toString cfg.stateVersion}; is not a valid value";
+    } ];
   };
 }