fix: evaluate environment-pass before environment, so environment can reference or override those variables

cibuildwheel/environment.py

@@ -124,8 +124,12 @@ def as_dictionary(
 
         return environment
 
-    def add(self, name: str, value: str) -> None:
-        self.assignments.append(EnvironmentAssignmentRaw(name=name, value=value))
+    def add(self, name: str, value: str, prepend: bool = False) -> None:
+        assignment = EnvironmentAssignmentRaw(name=name, value=value)
+        if prepend:
+            self.assignments.insert(0, assignment)
+        else:
+            self.assignments.append(assignment)
 
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({[repr(a) for a in self.assignments]!r})"

cibuildwheel/options.py

@@ -532,9 +532,9 @@ def build_options(self, identifier: str | None) -> BuildOptions:
 
             # Pass through environment variables
             if self.platform == "linux":
-                for env_var_name in environment_pass:
+                for env_var_name in reversed(environment_pass):
                     with contextlib.suppress(KeyError):
-                        environment.add(env_var_name, self.env[env_var_name])
+                        environment.add(env_var_name, self.env[env_var_name], prepend=True)
 
             if dependency_versions == "pinned":
                 dependency_constraints: None | (

unit_test/options_test.py

@@ -255,6 +255,25 @@ def test_container_engine_option(tmp_path: Path, toml_assignment, result_name, r
     assert parsed_container_engine.create_args == result_create_args
 
 
+def test_environment_pass_references():
+    options = Options(
+        platform="linux",
+        command_line_arguments=CommandLineArguments.defaults(),
+        env={
+            "CIBW_ENVIRONMENT_PASS_LINUX": "STARTER MAIN_COURSE",
+            "STARTER": "green eggs",
+            "MAIN_COURSE": "ham",
+            "CIBW_ENVIRONMENT": 'MEAL="$STARTER and $MAIN_COURSE"',
+        },
+    )
+    parsed_environment = options.build_options(identifier=None).environment
+    assert parsed_environment.as_dictionary(prev_environment={}) == {
+        "MEAL": "green eggs and ham",
+        "STARTER": "green eggs",
+        "MAIN_COURSE": "ham",
+    }
+
+
 @pytest.mark.parametrize(
     ("toml_assignment", "result_name", "result_args"),
     [