WIP: opt-out, inputs.self.outPathIsString = true;

NixOS · Aug 8, 2024 · 23d8c06 · 23d8c06
1 parent e21e54e
commit 23d8c06
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Showing 2 changed files with 41 additions and 17 deletions.
diff --git a/src/libexpr/flake/call-flake.nix b/src/libexpr/flake/call-flake.nix
@@ -37,29 +37,42 @@ let
     builtins.mapAttrs
       (key: node:
         let
-
-          sourceInfo =
+          # FIXME: remove obsolete node.info.
+          tree0 =
             if overrides ? ${key}
             then
               overrides.${key}.sourceInfo
             else
-              # FIXME: remove obsolete node.info.
-              let
-                tree = 
-                  fetchTree (node.info or {} // removeAttrs node.locked ["dir"]);
-              in tree // {
-                # TODO: return the path value without fetching to the store?
-                #       removing this will improve performance, but may break
-                #       one or two flakes, that rely on
-                #       `builtins.typeOf outPath` for some reason, or perhaps
-                #       something more subtle than that, despite our conservative
-                #       choice of lazy path semantics.
-                outPath = "${tree.outPath}";
-              };
+              fetchTree (node.info or {} // removeAttrs node.locked [
+                # attributes that are applied after fetching
+                "dir"
+                "outPathIsString"
+              ]);
+
+          # TODO: split this logic into stand-alone functions
+          getSourceInfo = coerceOutPathToString:
+            tree0 // {
+              # TODO: return the path value without fetching to the store?
+              #       removing this will improve performance, but may break
+              #       one or two flakes, that rely on
+              #       `builtins.typeOf outPath` for some reason, or perhaps
+              #       something more subtle than that, despite our conservative
+              #       choice of lazy path semantics.
+              outPath = if coerceOutPathToString then "${tree0.outPath}" else tree0.outPath;
+            };
 
           subdir = overrides.${key}.dir or node.locked.dir or "";
 
-          outPath = sourceInfo + ((if subdir == "" then "" else "/") + subdir);
+          getOutPath = coerceOutPathToString:
+            getSourceInfo coerceOutPathToString + ((if subdir == "" then "" else "/") + subdir);
+
+          outPath = getOutPath outPathIsString;
+          sourceInfo = getSourceInfo outPathIsString;
+
+          flake0 = import (getOutPath false + "/flake.nix");
+
+          # Users can opt in to the legacy behavior of outPath being a string.
+          outPathIsString = flake0.inputs.self.outPathIsString or false;
 
           flake = import (outPath + "/flake.nix");
 

diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
@@ -118,6 +118,8 @@ static FlakeInput parseFlakeInput(
         }
     else {
         attrs.erase("url");
+        // TODO: if (isRoot) ...
+        attrs.erase("outPathIsString");
         if (!attrs.empty())
             throw Error("unexpected flake input attribute '%s', at %s", attrs.begin()->first, state.positions[pos]);
         if (url)
@@ -411,7 +413,16 @@ LockedFlake lockFlake(
                from what's in the lock file). */
             for (auto & [id, input2] : flakeInputs) {
                 auto inputPath(inputPathPrefix);
-                inputPath.push_back(id);
+                if (id == "self") {
+                    // TODO validate that it only has `outPathIsString` (for now)
+                    // TODO accept hints for fetching schemas such as `git` or `github`
+                    //      so that the fetching of the flake can be customized as
+                    //      needed in the flake itself.
+                    // TODO allow certain schemas to be rejected, e.g. inputs.self.hints."github" = throw "this flake must be fetch with the `git:` scheme in order to load submodules";
+                    continue;
+                } else {
+                    inputPath.push_back(id);
+                }
                 auto inputPathS = printInputPath(inputPath);
                 debug("computing input '%s'", inputPathS);