feat(cli): support multiple constraints files via repeated -c flag

src/fromager/__main__.py

@@ -134,7 +134,8 @@
     "-c",
     "--constraints-file",
     type=str,
-    help="location of the constraints file",
+    multiple=True,
+    help="location of constraint file(s), may be repeated",
 )
 @click.option(
     "--cleanup/--no-cleanup",
@@ -177,7 +178,7 @@ def main(
     patches_dir: pathlib.Path,
     settings_file: pathlib.Path,
     settings_dir: pathlib.Path,
-    constraints_file: str,
+    constraints_file: tuple[str, ...],
     cleanup: bool,
     variant: str,
     jobs: int | None,
@@ -247,7 +248,7 @@ def main(
             logger.info(f"variant: {variant}")
             logger.info(f"patches dir: {patches_dir}")
             logger.info(f"maximum concurrent jobs: {jobs}")
-            logger.info(f"constraints file: {constraints_file}")
+            logger.info(f"constraints file(s): {constraints_file}")
             logger.info(f"network isolation: {network_isolation}")
             if build_wheel_server_url:
                 logger.info(f"external build wheel server: {build_wheel_server_url}")

src/fromager/context.py

@@ -19,7 +19,6 @@
     dependency_graph,
     external_commands,
     packagesettings,
-    request_session,
 )
 
 if typing.TYPE_CHECKING:
@@ -36,7 +35,7 @@ class WorkContext:
     def __init__(
         self,
         active_settings: packagesettings.Settings | None,
-        constraints_file: str | None,
+        constraints_file: str | tuple[str, ...] | None,
         patches_dir: pathlib.Path,
         sdists_repo: pathlib.Path,
         wheels_repo: pathlib.Path,
@@ -59,13 +58,16 @@ def __init__(
                 max_jobs=max_jobs,
             )
         self.settings = active_settings
-        self.input_constraints_uri: str | None
         self.constraints = constraints.Constraints()
-        if constraints_file is not None:
-            self.input_constraints_uri = constraints_file
-            self.constraints.load_constraints_file(constraints_file)
-        else:
-            self.input_constraints_uri = None
+        self.input_constraints_uris: list[str] = []
+        if constraints_file:
+            if isinstance(constraints_file, str):
+                files: tuple[str, ...] = (constraints_file,)
+            else:
+                files = constraints_file
+            for cf in files:
+                self.input_constraints_uris.append(cf)
+                self.constraints.load_constraints_file(cf)
         self.sdists_repo = pathlib.Path(sdists_repo).resolve()
         self.sdists_downloads = self.sdists_repo / "downloads"
         self.sdists_builds = self.sdists_repo / "builds"
@@ -135,16 +137,16 @@ def pip_wheel_server_args(self) -> list[str]:
 
     @property
     def pip_constraint_args(self) -> list[str]:
-        if not self.input_constraints_uri:
+        if not self.input_constraints_uris:
             return []
 
-        if self.input_constraints_uri.startswith(("https://", "http://", "file://")):
-            path_to_constraints_file = self.work_dir / "input-constraints.txt"
-            if not path_to_constraints_file.exists():
-                response = request_session.session.get(self.input_constraints_uri)
-                path_to_constraints_file.write_text(response.text)
-        else:
-            path_to_constraints_file = pathlib.Path(self.input_constraints_uri)
+        path_to_constraints_file = self.work_dir / "input-constraints.txt"
+        lines: list[str] = []
+        for constraint_name in self.constraints:
+            req = self.constraints.get_constraint(constraint_name)
+            if req is not None:
+                lines.append(f"{req}\n")
+        path_to_constraints_file.write_text("".join(lines), encoding="utf-8")
 
         path_to_constraints_file = path_to_constraints_file.absolute()
         return ["--constraint", os.fspath(path_to_constraints_file)]

tests/test_cli.py

@@ -96,6 +96,34 @@ def test_output_dir_overridden_by_explicit_flags(
     assert not (out / "sdists-repo").exists()
 
 
+def test_multiple_constraints_files(
+    tmp_path: pathlib.Path, cli_runner: CliRunner
+) -> None:
+    """Multiple -c flags are accepted and constraints are merged."""
+    file1 = tmp_path / "base.txt"
+    file1.write_text("numpy>=1.24\n")
+    file2 = tmp_path / "extra.txt"
+    file2.write_text("numpy<2.0\n")
+
+    out = tmp_path / "output"
+    out.mkdir()
+
+    result = cli_runner.invoke(
+        fromager,
+        [
+            "-O",
+            str(out),
+            "-c",
+            str(file1),
+            "-c",
+            str(file2),
+            "canonicalize",
+            "some-package",
+        ],
+    )
+    assert result.exit_code == 0, result.output
+
+
 KNOWN_COMMANDS: set[str] = {
     "bootstrap",
     "bootstrap-parallel",

tests/test_context.py

@@ -10,7 +10,7 @@
 
 def _make_context(
     tmp_path: pathlib.Path,
-    constraints_file: str | None = None,
+    constraints_file: str | tuple[str, ...] | None = None,
     wheel_server_url: str = "",
     cleanup: bool = True,
 ) -> context.WorkContext:
@@ -43,16 +43,40 @@ def _all_setup_dirs(ctx: context.WorkContext) -> list[pathlib.Path]:
 
 def test_pip_constraints_args(tmp_path: pathlib.Path) -> None:
     constraints_file = tmp_path / "constraints.txt"
-    constraints_file.write_text("\n")  # the file has to exist
+    constraints_file.write_text("numpy>=1.24\n")
     ctx = _make_context(tmp_path, constraints_file=str(constraints_file))
     ctx.setup()
-    assert ["--constraint", os.fspath(constraints_file)] == ctx.pip_constraint_args
+    merged_path = ctx.work_dir / "input-constraints.txt"
+    assert ["--constraint", os.fspath(merged_path)] == ctx.pip_constraint_args
+    assert merged_path.exists()
+    assert "numpy>=1.24" in merged_path.read_text()
 
     ctx = _make_context(tmp_path)
     ctx.setup()
     assert [] == ctx.pip_constraint_args
 
 
+def test_pip_constraints_args_multiple_files(tmp_path: pathlib.Path) -> None:
+    file1 = tmp_path / "base.txt"
+    file1.write_text("numpy>=1.24\n")
+    file2 = tmp_path / "security.txt"
+    file2.write_text("numpy<2.0\nrequests>=2.28\n")
+
+    ctx = _make_context(tmp_path, constraints_file=(str(file1), str(file2)))
+    ctx.setup()
+    merged_path = ctx.work_dir / "input-constraints.txt"
+    assert ["--constraint", os.fspath(merged_path)] == ctx.pip_constraint_args
+    content = merged_path.read_text()
+    lines = [line for line in content.splitlines() if line.strip()]
+    numpy_lines = [line for line in lines if line.startswith("numpy")]
+    assert len(numpy_lines) == 1
+    assert ">=1.24" in numpy_lines[0]
+    assert "<2.0" in numpy_lines[0]
+    requests_lines = [line for line in lines if line.startswith("requests")]
+    assert len(requests_lines) == 1
+    assert ">=2.28" in requests_lines[0]
+
+
 def test_setup_creates_directories(tmp_path: pathlib.Path) -> None:
     ctx = _make_context(tmp_path)
     ctx.setup()