libstore/build: fix URL guesswork for failing structuredAttrs FODs

Fixes #1175

Change-Id: I6a074f489620f6de0615858f4d0d872c6a6a6964

doc/manual/change-authors.yml

@@ -150,6 +150,9 @@ kasimeka:
   forgejo: janw4ld
   github: kasimeka
 
+keysmashes:
+  github: keysmashes
+
 kfears:
   display_name: KFears
   forgejo: kfearsoff

doc/manual/rl-next/structuredattrs-url-guesswork.md

@@ -0,0 +1,11 @@
+---
+synopsis: "Hash mismatch diagnostics now work with `structuredAttrs`"
+issues: [fj#1175]
+cls: [5441]
+category: Fixes
+credits: [keysmashes]
+---
+
+Nixpkgs fetchers like `fetchurl` now use `structuredAttrs`, which broke the
+hash mismatch diagnostics added in Lix 2.91. This has been fixed and the likely
+URL is now shown again.

lix/libstore/build/local-derivation-goal.cc

@@ -1711,6 +1711,23 @@ try {
                     anyHashMismatchSeen = true;
                     // XXX: shameless layering violation hack that makes the hash mismatch error at least not utterly worthless
                     auto guessedUrl = getOr(drv->env, "urls", getOr(drv->env, "url", "(unknown)"));
+                    if (guessedUrl == "(unknown)") {
+                        if (auto structuredAttrs = parsedDrv->getStructuredAttrs()) {
+                            auto json = *structuredAttrs;
+                            if (json.contains("urls") && json["urls"].is_array() && !json["urls"].empty()) {
+                                guessedUrl = "";
+                                for (auto it = json["urls"].begin(); it != json["urls"].end(); ++it) {
+                                    if (!it->is_string()) continue;
+                                    if (guessedUrl != "") {
+                                        guessedUrl += " or ";
+                                    }
+                                    guessedUrl += it->get<std::string>();
+                                }
+                            } else if (json.contains("url") && json["url"].is_string()) {
+                                guessedUrl = json["url"].get<std::string>();
+                            }
+                        }
+                    }
                     delayedException = std::make_exception_ptr(BuildError(
                         "hash mismatch in fixed-output derivation '%s':\n    likely URL: %s\n     "
                         "specified: %s\n           got: %s\n expected path: %s\n      got path: %s",

tests/functional2/commands/test_build/assets/test_build/fod-failing.nix

@@ -38,4 +38,37 @@ rec {
         exit 1
       '';
   };
+  x5 = mkDerivation {
+    name = "x5";
+    __structuredAttrs = true;
+    buildCommand = "echo $name > \${outputs[out]}";
+    url = "https://avian.example/owls.tar.gz";
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
+  x6 = mkDerivation {
+    name = "x6";
+    __structuredAttrs = true;
+    buildCommand = "echo $name > \${outputs[out]}";
+    urls = [ "https://avian.example/geese.tar.gz" ];
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
+  x7 = mkDerivation {
+    name = "x7";
+    __structuredAttrs = true;
+    buildCommand = "echo $name > \${outputs[out]}";
+    url = 42;
+    urls = 0;
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
+  x8 = mkDerivation {
+    name = "x8";
+    __structuredAttrs = true;
+    buildCommand = "echo $name > \${outputs[out]}";
+    urls = [ "https://avian.example/swan1.tar.gz" "https://avian.example/swan2.tar.gz" ];
+    outputHashMode = "recursive";
+    outputHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  };
 }

tests/functional2/commands/test_build/test_build_fod.py

@@ -1,5 +1,7 @@
 import re
 
+import pytest
+
 from testlib.fixtures.file_helper import with_files, CopyFile
 from testlib.fixtures.nix import Nix
 from testlib.utils import get_global_asset
@@ -27,8 +29,7 @@ def test_url_keep_going_1(nix: Nix):
     assert re.findall(r"hash mismatch in fixed-output derivation '.*-x.\.drv'", err)
     assert "likely URL: " in err
     assert re.findall(
-        r"error: build of '.*-x[1-4]\.drv\^out', '.*-x[1-4]\.drv\^out', '.*-x[1-4]\.drv\^out', '.*-x[1-4]\.drv\^out' failed",
-        err,
+        r"error: build of '.*-x[1-8]\.drv\^out'(, '.*-x[1-7]\.drv\^out'){6} failed", err
     )
 
 
@@ -67,6 +68,23 @@ def test_missing_dependency_keep_going(nix: Nix):
         assert re.findall(rf"hash mismatch in fixed-output derivation '.*-{f}\.drv'", err)
 
 
+@with_files(_fod_files)
+@pytest.mark.parametrize(
+    ("attr", "url"),
+    [
+        ("x5", "https://avian.example/owls.tar.gz"),
+        ("x6", "https://avian.example/geese.tar.gz"),
+        ("x7", "(unknown)"),
+        ("x8", "https://avian.example/swan1.tar.gz or https://avian.example/swan2.tar.gz"),
+    ],
+)
+def test_structured_attrs_url(nix: Nix, attr: str, url: str):
+    res = nix.nix([*_build_args, attr], flake=True).run().expect(1)
+    err = res.stderr_plain
+    assert err.count("error: ") == 1
+    assert f"likely URL: {url}" in err
+
+
 @with_files({"config.nix": get_global_asset("config.nix")})
 def test_build_inaccessible_build_dir(nix: Nix):
     env = nix.env