fix(bootstrap): auto-disable constraints and extend e2e test coverage

e2e/test_bootstrap_multiple_versions.sh

@@ -7,18 +7,21 @@
 SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 source "$SCRIPTDIR/common.sh"
 
-# Create constraints file to pin build dependencies (keeps CI fast)
+# Create constraints file with generous ranges to test multiple versions
+# of build dependencies (not just top-level packages)
 constraints_file=$(mktemp)
 trap "rm -f $constraints_file" EXIT
 cat > "$constraints_file" <<EOF
-flit-core==3.11.0
+# Allow a range of flit-core versions to verify multiple-versions works for dependencies
+flit-core>=3.9,<3.12
 EOF
 
 # Use tomli with a version range that matches exactly 3 versions (2.0.0, 2.0.1, 2.0.2)
 # tomli has no runtime dependencies, making it fast to bootstrap
-# It uses flit-core as build backend (pinned above)
+# It uses flit-core as build backend, and we allow multiple flit-core versions
+# to test that --multiple-versions works for the entire dependency chain
 # Using <=2.0.2 instead of <2.1 to be deterministic (tomli 2.1.0 exists)
-# Note: constraints file generation will fail (expected with multiple versions)
+# Note: constraints file generation is automatically disabled with --multiple-versions
 fromager \
   --log-file="$OUTDIR/bootstrap.log" \
   --error-log-file="$OUTDIR/fromager-errors.log" \
@@ -28,7 +31,7 @@ fromager \
   --constraints-file="$constraints_file" \
   bootstrap \
   --multiple-versions \
-  'tomli>=2.0,<=2.0.2' || true
+  'tomli>=2.0,<=2.0.2'
 
 # Check that wheels were built
 echo "Checking for wheels..."
@@ -60,3 +63,22 @@ fi
 
 echo ""
 echo "SUCCESS: All expected tomli versions (2.0.0, 2.0.1, 2.0.2) were bootstrapped"
+
+# Verify that multiple versions of flit-core were built (dependency of tomli)
+# This confirms that --multiple-versions works for the entire dependency chain
+echo ""
+echo "Checking for flit-core versions (build dependency)..."
+FLIT_CORE_COUNT=$(find "$OUTDIR/wheels-repo/downloads/" -name 'flit_core-3.*.whl' | wc -l)
+echo "Found $FLIT_CORE_COUNT flit-core 3.x wheel(s)"
+
+if [ "$FLIT_CORE_COUNT" -lt 2 ]; then
+  echo ""
+  echo "ERROR: Expected at least 2 flit-core versions, found $FLIT_CORE_COUNT"
+  echo "The --multiple-versions flag should bootstrap multiple versions of dependencies too"
+  echo ""
+  echo "Found flit-core wheels:"
+  find "$OUTDIR/wheels-repo/downloads/" -name 'flit_core-*.whl'
+  exit 1
+fi
+
+echo "✓ Multiple versions of flit-core were bootstrapped (confirms dependency chain handling)"

src/fromager/commands/bootstrap.py

@@ -159,6 +159,14 @@ def bootstrap(
         logger.info(
             "multiple versions mode enabled: will bootstrap all matching versions"
         )
+        # Automatically disable constraints when multiple versions mode is enabled
+        # because constraints.txt cannot handle multiple versions of the same package
+        if not skip_constraints:
+            logger.info(
+                "automatically disabling constraints generation "
+                "(incompatible with --multiple-versions)"
+            )
+            skip_constraints = True
 
     pre_built = wkctx.settings.list_pre_built()
     if pre_built:

tests/test_bootstrap.py

@@ -1,4 +1,5 @@
 import io
+import logging
 import pathlib
 import textwrap
 from unittest.mock import Mock, patch
@@ -541,6 +542,143 @@ def test_skip_constraints_cli_option() -> None:
     assert "Skip generating constraints.txt file" in result.output
 
 
+@patch("fromager.commands.bootstrap.bootstrapper.Bootstrapper")
+@patch("fromager.commands.bootstrap.server.start_wheel_server")
+@patch("fromager.commands.bootstrap.progress.progress_context")
+@patch("fromager.commands.bootstrap.metrics.summarize")
+def test_multiple_versions_auto_disables_constraints(
+    mock_metrics: Mock,
+    mock_progress: Mock,
+    mock_server: Mock,
+    mock_bootstrapper: Mock,
+    tmp_context: context.WorkContext,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test that --multiple-versions alone auto-disables constraints and logs message"""
+    # Setup mocks
+    mock_progress.return_value.__enter__.return_value = Mock()
+    mock_progress.return_value.__exit__.return_value = None
+    mock_bt_instance = Mock()
+    mock_bt_instance.resolve_and_add_top_level.return_value = ("url", Version("1.0"))
+    mock_bt_instance.finalize.return_value = 0
+    mock_bootstrapper.return_value = mock_bt_instance
+
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        # Create a temporary requirements file
+        pathlib.Path("req.txt").write_text("setuptools>=60\n")
+
+        # Invoke with --multiple-versions but NOT --skip-constraints
+        with caplog.at_level(logging.INFO):
+            result = runner.invoke(
+                bootstrap.bootstrap,
+                [
+                    "-r",
+                    "req.txt",
+                    "--multiple-versions",
+                ],
+                obj=tmp_context,
+            )
+
+        # Should succeed
+        assert result.exit_code == 0
+
+        # Should log that constraints are auto-disabled
+        assert "automatically disabling constraints generation" in caplog.text
+        assert "incompatible with --multiple-versions" in caplog.text
+
+
+@patch("fromager.commands.bootstrap.bootstrapper.Bootstrapper")
+@patch("fromager.commands.bootstrap.server.start_wheel_server")
+@patch("fromager.commands.bootstrap.progress.progress_context")
+@patch("fromager.commands.bootstrap.metrics.summarize")
+def test_multiple_versions_with_skip_constraints_no_duplicate_log(
+    mock_metrics: Mock,
+    mock_progress: Mock,
+    mock_server: Mock,
+    mock_bootstrapper: Mock,
+    tmp_context: context.WorkContext,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test that --multiple-versions --skip-constraints together doesn't log auto-disable message"""
+    # Setup mocks
+    mock_progress.return_value.__enter__.return_value = Mock()
+    mock_progress.return_value.__exit__.return_value = None
+    mock_bt_instance = Mock()
+    mock_bt_instance.resolve_and_add_top_level.return_value = ("url", Version("1.0"))
+    mock_bt_instance.finalize.return_value = 0
+    mock_bootstrapper.return_value = mock_bt_instance
+
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        # Create a temporary requirements file
+        pathlib.Path("req.txt").write_text("setuptools>=60\n")
+
+        # Invoke with BOTH --multiple-versions AND --skip-constraints
+        with caplog.at_level(logging.INFO):
+            result = runner.invoke(
+                bootstrap.bootstrap,
+                [
+                    "-r",
+                    "req.txt",
+                    "--multiple-versions",
+                    "--skip-constraints",
+                ],
+                obj=tmp_context,
+            )
+
+        # Should succeed
+        assert result.exit_code == 0
+
+        # Should NOT log the auto-disable message (already disabled by user)
+        assert "automatically disabling constraints generation" not in caplog.text
+
+
+@patch("fromager.commands.bootstrap.bootstrapper.Bootstrapper")
+@patch("fromager.commands.bootstrap.server.start_wheel_server")
+@patch("fromager.commands.bootstrap.progress.progress_context")
+@patch("fromager.commands.bootstrap.metrics.summarize")
+@patch("fromager.commands.bootstrap.write_constraints_file")
+def test_without_multiple_versions_constraints_not_disabled(
+    mock_write_constraints: Mock,
+    mock_metrics: Mock,
+    mock_progress: Mock,
+    mock_server: Mock,
+    mock_bootstrapper: Mock,
+    tmp_context: context.WorkContext,
+) -> None:
+    """Test that without --multiple-versions, constraints are not auto-disabled"""
+    # Setup mocks
+    mock_progress.return_value.__enter__.return_value = Mock()
+    mock_progress.return_value.__exit__.return_value = None
+    mock_bt_instance = Mock()
+    mock_bt_instance.resolve_and_add_top_level.return_value = ("url", Version("1.0"))
+    mock_bt_instance.finalize.return_value = 0
+    mock_bootstrapper.return_value = mock_bt_instance
+    mock_write_constraints.return_value = True
+
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        # Create a temporary requirements file
+        pathlib.Path("req.txt").write_text("setuptools>=60\n")
+
+        # Invoke WITHOUT --multiple-versions
+        result = runner.invoke(
+            bootstrap.bootstrap,
+            [
+                "-r",
+                "req.txt",
+            ],
+            obj=tmp_context,
+        )
+
+        # Should succeed
+        assert result.exit_code == 0
+
+        # write_constraints_file should have been called (constraints NOT disabled)
+        assert mock_write_constraints.called
+
+
 @patch("fromager.gitutils.git_clone")
 def test_resolve_version_from_git_url_with_submodules_enabled(
     mock_git_clone: Mock,