replace-workspace-values.py: fix missing key exception

If a cargo workspace member defines a key with `.workpace = true` but
this key does not exist in the workspace manifest, the script was
raising an exception. The case is now handled properly.

pkgs/build-support/rust/replace-workspace-values.py

@@ -31,7 +31,12 @@ def replace_key(
         local_dep = table[key]
         del local_dep["workspace"]
 
-        workspace_dep = workspace_manifest[section][key]
+        try:
+            workspace_dep = workspace_manifest[section][key]
+        except KeyError:
+            # Key is not present in workspace manifest, we can't inherit the value, so we mark it for deletion
+            table[key] = {}
+            return True
 
         if section == "dependencies":
             if isinstance(workspace_dep, str):
@@ -104,10 +109,18 @@ def main() -> None:
 
     changed = False
 
+    to_remove = []
     for key in crate_manifest["package"].keys():
-        changed |= replace_key(
+        changed_key = replace_key(
             workspace_manifest, crate_manifest["package"], "package", key
         )
+        if changed_key and crate_manifest["package"][key] == {}:
+            # Key is missing from workspace manifest, mark for deletion
+            to_remove.append(key)
+        changed |= changed_key
+    # Remove keys which have no value
+    for key in to_remove:
+        del crate_manifest["package"][key]
 
     changed |= replace_dependencies(workspace_manifest, crate_manifest)
 

pkgs/build-support/rust/test/import-cargo-lock/git-dependency-workspace-inheritance/crate_missing_field.toml

@@ -0,0 +1,13 @@
+[package]
+name = "im_using_workspaces"
+version = { workspace = true }
+publish = false
+readme.workspace = true
+keywords = [
+    "workspace",
+    "other_thing",
+    "third_thing",
+]
+
+[dependencies]
+bar = "1.0.0"

pkgs/build-support/rust/test/import-cargo-lock/git-dependency-workspace-inheritance/default.nix

@@ -8,4 +8,8 @@ runCommand "git-dependency-workspace-inheritance-test" { } ''
   cp --no-preserve=mode ${./crate_lints.toml} "$out"
   ${replaceWorkspaceValues} "$out" ${./workspace.toml}
   diff -u "$out" ${./want_lints.toml}
+
+  cp --no-preserve=mode ${./crate_missing_field.toml} "$out"
+  ${replaceWorkspaceValues} "$out" ${./workspace.toml}
+  diff -u "$out" ${./want_missing_field.toml}
 ''

pkgs/build-support/rust/test/import-cargo-lock/git-dependency-workspace-inheritance/want_missing_field.toml

@@ -0,0 +1,12 @@
+[package]
+name = "im_using_workspaces"
+version = "1.0.0"
+publish = false
+keywords = [
+    "workspace",
+    "other_thing",
+    "third_thing",
+]
+
+[dependencies]
+bar = "1.0.0"