feat(bootstrapper): run phase items in parallel when possible

e2e/ci_bootstrap_parallel_suite.sh

@@ -15,5 +15,6 @@ test_section "bootstrap parallel tests"
 run_test "bootstrap_parallel"
 run_test "bootstrap_parallel_git_url"
 run_test "bootstrap_parallel_git_url_tag"
+run_test "bootstrap_parallel_multiple_versions"
 
 finish_suite

e2e/test_bootstrap_parallel_multiple_versions.sh

@@ -0,0 +1,97 @@
+#!/bin/bash
+# -*- indent-tabs-mode: nil; tab-width: 2; sh-indentation: 2; -*-
+
+# Test bootstrap-parallel with --multiple-versions flag.
+# Bootstraps flit-core 3.0.0 through 3.12.0 inclusive (many versions) with
+# only 5 parallel workers to verify that batches larger than the worker pool
+# are handled correctly.
+#
+# Note: flit-core <3.10.0 uses ast.Str which was removed in Python 3.14 and
+# will fail during GET_BUILD_DEPS; those failures are expected and handled
+# gracefully by the bootstrapper.  The test only asserts that the versions
+# that *can* build (>=3.10.0) are present in the output.
+
+SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+source "$SCRIPTDIR/common.sh"
+
+# Constrain flit-core (its own build backend) to the same range so the
+# resolver never pulls in a version outside 3.0.0–3.12.0 as a build dep.
+constraints_file=$(mktemp)
+trap 'rm -f "$constraints_file"; on_exit' EXIT
+cat > "$constraints_file" <<EOF
+flit-core>=3.0.0,<=3.12.0
+setuptools==82.0.1
+poetry-core==2.4.0
+tomli==2.4.1
+toml==0.10.2
+EOF
+
+fromager \
+  --log-file="$OUTDIR/bootstrap.log" \
+  --error-log-file="$OUTDIR/fromager-errors.log" \
+  --sdists-repo="$OUTDIR/sdists-repo" \
+  --wheels-repo="$OUTDIR/wheels-repo" \
+  --work-dir="$OUTDIR/work-dir" \
+  --constraints-file="$constraints_file" \
+  bootstrap-parallel \
+  --multiple-versions \
+  --max-workers 5 \
+  'flit-core>=3.0.0,<=3.12.0'
+
+echo "Checking for flit-core wheels..."
+find "$OUTDIR/wheels-repo/downloads/" -name 'flit_core-*.whl' | sort
+
+# Verify that a representative sample of versions that can build on this
+# Python (>=3.10.0, which dropped ast.Str) were bootstrapped.
+# flit-core 3.0.0 through 3.12.0 includes many releases; 3.10.0–3.12.0
+# are the ones compatible with Python 3.14+.
+EXPECTED_VERSIONS="3.10.0 3.11.0 3.12.0"
+MISSING_VERSIONS=""
+
+for version in $EXPECTED_VERSIONS; do
+  if find "$OUTDIR/wheels-repo/downloads/" -name "flit_core-${version}-*.whl" | grep -q .; then
+    echo "found wheel for flit-core $version"
+  else
+    echo "missing wheel for flit-core $version" 1>&2
+    MISSING_VERSIONS="$MISSING_VERSIONS $version"
+  fi
+done
+
+if [ -n "$MISSING_VERSIONS" ]; then
+  echo "" 1>&2
+  echo "ERROR: Missing expected versions:$MISSING_VERSIONS" 1>&2
+  echo "The --multiple-versions flag should have bootstrapped all matching versions" 1>&2
+  echo "" 1>&2
+  echo "Found flit-core wheels:" 1>&2
+  find "$OUTDIR/wheels-repo/downloads/" -name 'flit_core-*.whl' 1>&2
+  exit 1
+fi
+
+# Verify that the phases expected to parallelize each logged at least one
+# "starting parallel batch" line, confirming the parallel code path ran.
+#
+# Note: "resolve" is intentionally excluded — with a single top-level
+# requirement there is only one resolve item so that phase always runs serially.
+PARALLEL_PHASES="start prepare-source get-build-deps build process-install-deps complete"
+PHASES_WITHOUT_PARALLEL_BATCH=""
+
+echo ""
+echo "Checking that parallel phases ran at least one parallel batch..."
+for phase in $PARALLEL_PHASES; do
+  if grep -q "starting parallel batch: phase=${phase} " "$OUTDIR/bootstrap.log" 2>/dev/null; then
+    echo "phase=${phase}: OK (parallel batch confirmed)"
+  else
+    echo "phase=${phase}: MISSING parallel batch" 1>&2
+    PHASES_WITHOUT_PARALLEL_BATCH="${PHASES_WITHOUT_PARALLEL_BATCH} ${phase}"
+  fi
+done
+
+if [ -n "$PHASES_WITHOUT_PARALLEL_BATCH" ]; then
+  echo "" 1>&2
+  echo "ERROR: these phases never ran a parallel batch:${PHASES_WITHOUT_PARALLEL_BATCH}" 1>&2
+  exit 1
+fi
+
+echo "OK: all parallel phases ran at least one parallel batch"
+echo ""
+echo "SUCCESS: All sampled flit-core versions (3.10.0–3.12.0) were bootstrapped (from 3.0.0–3.12.0 range with 5 workers)"

e2e/test_rust_vendor.sh

@@ -15,6 +15,8 @@ VERSION="1.6.0"
 # Bootstrap the test project
 fromager \
     $NETWORK_ISOLATION \
+    --log-file="$OUTDIR/bootstrap.log" \
+    --error-log-file="$OUTDIR/fromager-errors.log" \
     --sdists-repo="$OUTDIR/sdists-repo" \
     --wheels-repo="$OUTDIR/wheels-repo" \
     --work-dir="$OUTDIR/work-dir" \