From fd1485d077c06414752a90d2aef84b09d8a4cca2 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Thu, 12 Nov 2026 02:33:44 +0000
Subject: populate: name inputs of generated flakes validly

Generated flakes used source names as input names, but Nix accepts fewer
names there than populate does, e.g. not alt-1.0 or self.  Following such
a source failed late, at locking, with an error mentioning neither krops
nor the source.  Names Nix doesn't accept get replaced by ones derived
from them.

An edge case follows a source named alt-1.0.
---
 pkgs/populate/default.nix | 21 ++++++++++++++-------
 tests/scenarios.nix       | 11 +++++++++++
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/pkgs/populate/default.nix b/pkgs/populate/default.nix
index 5939742..3e5f47b 100644
--- a/pkgs/populate/default.nix
+++ b/pkgs/populate/default.nix
@@ -57,6 +57,13 @@ let
     flakesDir = "${target.path}/.populate/flakes";
     generated = filterAttrs (_: source: flakeFollows source != []) sources;
     names = attrNames generated;
+    # Source names become input names in generated flakes, where Nix accepts
+    # fewer names than populate.  Others get replaced by one derived from
+    # them.
+    inputName = name:
+      if builtins.match "[a-zA-Z][a-zA-Z0-9_-]*" name != null && name != "self"
+        then name
+        else "source-${substring 0 16 (builtins.hashString "sha256" name)}";
     drawnFrom = name: map (x: x.source) (flakeFollows generated.${name});
     sorted = toposort (a: b: elem a (drawnFrom b)) names;
     # Generated flakes refer to each other's generated flakes, so they don't
@@ -88,12 +95,12 @@ let
           else (findFirst (y: y.path == parent) null follows).source;
         rest = if parent == null then x.path else drop (length parent) x.path;
       in
-        "inputs.${toJSON base}" +
+        "inputs.${toJSON (inputName base)}" +
         # A source with a generated flake has itself as input therein.
         optionalString (parent != null && generated ? ${base})
-          ".inputs.${toJSON base}" +
+          ".inputs.${toJSON (inputName base)}" +
         concatMapStrings (name: ".inputs.${toJSON name}") rest +
-        ".follows = ${toJSON x.source};";
+        ".follows = ${toJSON (inputName x.source)};";
     in /* sh */ ''
       (
         url=$(flake_url ${quote name})
@@ -105,19 +112,19 @@ let
         cd ${quote "${flakesDir}/${name}"}
         {
           echo '{'
-          printf '  inputs.%s.url = "%s";\n' ${quote (toJSON name)} "$url"
+          printf '  inputs.%s.url = "%s";\n' ${quote (toJSON (inputName name))} "$url"
           ${concatImapStrings (i: source: /* sh */ ''
-            printf '  inputs.%s.url = "%s";\n' ${quote (toJSON source)} "$url${toString i}"
+            printf '  inputs.%s.url = "%s";\n' ${quote (toJSON (inputName source))} "$url${toString i}"
             ${optionalString (!generated ? ${source}) /* sh */ ''
               if ! test -e "$(readlink -f ${quote "${target.path}/${source}"})"/flake.nix; then
-                printf '  inputs.%s.flake = false;\n' ${quote (toJSON source)}
+                printf '  inputs.%s.flake = false;\n' ${quote (toJSON (inputName source))}
               fi
             ''}
           '') drawn}
           ${concatMapStrings (x: /* sh */ ''
             printf '  %s\n' ${quote (override x)}
           '') follows}
-          printf '  outputs = inputs: inputs.%s;\n' ${quote (toJSON name)}
+          printf '  outputs = inputs: inputs.%s;\n' ${quote (toJSON (inputName name))}
           echo '}'
         } > flake.nix
         # Not just ., which Nix takes for the enclosing Git work tree, if any.
diff --git a/tests/scenarios.nix b/tests/scenarios.nix
index 0e54054..6dbb84d 100644
--- a/tests/scenarios.nix
+++ b/tests/scenarios.nix
@@ -945,6 +945,17 @@ assert !(krops.isLocalTarget (targets.remote "/"));
         }
       ];
     })
+    (s "source-name" {
+      phases = twice {
+        sources = {
+          "alt-1.0".file = "/fixtures/alt";
+          x.file = { path = "/fixtures/filesrc"; inputs.dep.follows = "alt-1.0"; };
+        };
+        check = ''
+          expect_eq msg "$(nix_eval_online "$T"/.populate/flakes/x#msg)" top:alt,sub
+        '';
+      };
+    })
   ] ++ lib.optional (targetKind == "local")
     # The target has the path the input is locked to.
     (s "uselocal" {
-- 
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