libfetchers: ensure that lastModified is a uint64_t

When lastModified comes via inputFromAttrs it ends up as string in the
Attrs map. This results in:

error: input attribute 'lastModified' is not an integer

Fix by handling it like revCount, which already does the right thing.
If added a test and confirmed that it catches the issue.

Also kudos to alexander.sieg@cyberus-technology.de for helping with
debugging this!

Change-Id: I8378fcaea986d798cb8458d4e6e15c2a92c2520a

doc/manual/change-authors.yml

@@ -53,6 +53,10 @@ bb010g:
   forgejo: bb010g
   github: bb010g
 
+blitz:
+  display_name: Julian Stecklina
+  github: blitz
+
 cole-h:
   display_name: Cole Helbling
   github: cole-h
@@ -197,6 +201,9 @@ winter:
   forgejo: winter
   github: winterqt
 
+xanderio:
+  github: xanderio
+
 yshui:
   github: yshui
 

doc/manual/rl-next/last-modified.md

@@ -0,0 +1,17 @@
+---
+synopsis: "Fix handling of `lastModified` in tarball inputs"
+issues: []
+cls: [2792]
+category: Fixes
+credits: [xanderio, blitz]
+---
+
+Previous versions of Lix would fail with the following error, if a
+[tarball flake input](@docroot@/protocols/tarball-fetcher.md) redirect
+to a URL that contains a `lastModified` field:
+
+```
+error: input attribute 'lastModified' is not an integer
+```
+
+This is now fixed.

lix/libfetchers/tarball.cc

@@ -219,7 +219,7 @@ struct CurlInputScheme : InputScheme
 
         url.scheme = parseUrlScheme(url.scheme).transport;
 
-        emplaceURLQueryIntoAttrs(url, attrs, {"revCount"}, {});
+        emplaceURLQueryIntoAttrs(url, attrs, {"revCount", "lastModified"}, {});
 
         attrs.emplace("url", url.to_string());
         return inputFromAttrs(attrs);

tests/nixos/tarball-flakes.nix

@@ -3,6 +3,8 @@
 let
   pkgs = config.nodes.machine.nixpkgs.pkgs;
 
+  lastModified = builtins.toString nixpkgs.lastModified;
+
   root = pkgs.runCommand "nixpkgs-flake" {}
     ''
       mkdir -p $out/{stable,tags}
@@ -19,7 +21,7 @@ let
       # arbitrary headers.
       cat >$out/tags/.htaccess <<EOF
       Redirect "/tags/latest.tar.gz" "/stable/${nixpkgs.rev}.tar.gz"
-      Header always set Link "<http://localhost/stable/${nixpkgs.rev}.tar.gz?rev=${nixpkgs.rev}&revCount=1234>; rel=\"immutable\""
+      Header always set Link "<http://localhost/stable/${nixpkgs.rev}.tar.gz?rev=${nixpkgs.rev}&revCount=1234&lastModified=${lastModified}>; rel=\"immutable\""
       EOF
     '';
 in
@@ -69,23 +71,27 @@ in
 
     # Check that we got redirected to the immutable URL.
     locked_url = info["locked"]["url"]
-    assert locked_url == "http://localhost/stable/${nixpkgs.rev}.tar.gz?rev=${nixpkgs.rev}&revCount=1234", f"{locked_url=} != http://localhost/stable/${nixpkgs.rev}.tar.gz"
+    assert locked_url == "http://localhost/stable/${nixpkgs.rev}.tar.gz?lastModified=${lastModified}&rev=${nixpkgs.rev}&revCount=1234", f"{locked_url=} != http://localhost/stable/${nixpkgs.rev}.tar.gz"
 
-    # Check that we got the rev and revCount attributes.
+    # Check that we got the right attributes.
     revision = info["revision"]
     rev_count = info["revCount"]
+    last_modified = info["lastModified"]
     assert revision == "${nixpkgs.rev}", f"{revision=} != ${nixpkgs.rev}"
     assert rev_count == 1234, f"{rev_count=} != 1234"
+    assert last_modified == ${lastModified}, f"{last_modified=} != ${lastModified}"
 
     # Check that fetching with rev/revCount/narHash succeeds.
     machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?rev=" + revision)
     machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?revCount=" + str(rev_count))
     machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?narHash=" + info["locked"]["narHash"])
+    machine.succeed("nix flake metadata --json http://localhost/tags/latest.tar.gz?lastModified=" + str(last_modified))
 
     # Check that fetching fails if we provide incorrect attributes.
     machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?rev=493300eb13ae6fb387fbd47bf54a85915acc31c0")
     machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?revCount=789")
     machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?narHash=sha256-tbudgBSg+bHWHiHnlteNzN8TUvI80ygS9IULh4rklEw=")
+    machine.fail("nix flake metadata --json http://localhost/tags/latest.tar.gz?lastModified=1111111111")
   '';
 
 }