feat(deps): multi-version mangling — Level 1 fallback#19
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Sunrisepeak merged 1 commit intomainfrom May 9, 2026
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… coexistence When SemVer merge fails (typically two non-overlapping pins like =0.0.1 ⨯ =0.0.2 across two consumers of the same package), instead of hard-erroring the resolver now stages the secondary version's source under `target/.mangled/<consumer>/...` and rewrites its module declarations to a mangled name (`<X>__v<M>_<m>_<p>__mcpp`). The direct consumer's source is staged + rewritten too so its `import X;` points at the mangled secondary BMI. Both BMIs coexist in the build graph at distinct module names; C++23 module attachment isolates their internal symbols, so no namespace mangling is needed. Touches: - `src/pm/mangle.cppm` (new) — pure helper: name format + a regex-free source rewriter that handles `(export )?module X;`, `(export )?module X:Y;`, `(export )?import X;`, `import X:Y;`. Bare partition imports (`import :Y;`) and the global module fragment (`module ;`) are left intact. 11 new unit tests in `tests/unit/test_mangle.cpp`. - `src/cli.cppm` — resolver conflict branch: when `try_merge_semver` fails, run mangling instead of returning. WorkItem gains a `consumerDepIndex` field so the fallback can locate the consumer manifest for staging. Resolved record uses the mangled module name as `[package].name` so the modgraph validator's "module must be prefixed by package name" check passes. - `src/build/plan.cppm` + `ninja_backend.cppm` — when two compile units share a basename across packages (e.g. cmdline 0.0.1 and staged-mangled 0.0.2 both have `parse.cppm`), the colliding object paths get a per-package subdirectory (`obj/<sanitized-pkg>/<file>`). `.ddi` placement follows. Single-package builds keep the original `obj/<file>` layout so cache hashes don't churn. - `tests/e2e/33_multi_version_mangling.sh` (new) — Y-shape graph: libA pinned to cmdline 0.0.1, libB pinned to cmdline 0.0.2; the build succeeds with both BMIs (`mcpplibs.cmdline.gcm` + `mcpplibs.cmdline__v0_0_2__mcpp.gcm`) on disk and the runtime output matches. - `tests/e2e/32_semver_merge.sh` — drop the previously-irreconcilable case; that's now Level 1's territory and is covered by test 33. MVP scope (clear errors out of bounds): - Conflicting consumer must be a dep, not the main package. - Secondary version must be a leaf (no own transitive deps). Both surfaces are documented in the error message so users know which limit they hit and have a workaround (pin one version). CHANGELOG 0.0.3 entry: covers all three resolution levels (transitive walker / SemVer merge / mangling) and the obj-path-namespacing side-fix to the build backend.
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Summary
Layer 1 of the 0.0.3 dep-resolution work. Wraps up the three-step strategy on
mainalong with PR #17 (transitive walker) and PR #18 (SemVer merge).When the SemVer merger can't find a single version satisfying every consumer (typically
=0.0.1⨯=0.0.2or any genuine cross-major split), the resolver no longer hard-errors. Instead it stages the secondary version's source undertarget/.mangled/<consumer>/..., rewrites(export )?module X;/(export )?import X;to a mangled name (<X>__v<M>_<m>_<p>__mcpp), and the direct consumer is staged + rewritten too so itsimportpoints at the mangled BMI. Both BMIs coexist in the build graph at distinct module names; C++23 module attachment handles ABI isolation, so no namespace mangling is needed.Pieces
src/pm/mangle.cppm— pure helper (name format + regex-free source rewriter), 11 unit testscli.cppmresolver conflict branch — invokes mangling ontry_merge_semverfailure; tracksconsumerDepIndexper WorkItem; renames the staged secondary's[package].nameso the modgraph validator's prefix check passesbuild/plan.cppm+ninja_backend.cppm— basename-collision detection: when two compile units across packages share a filename (e.g. cmdline 0.0.1 and staged-mangled 0.0.2 both haveparse.cppm), colliding objects getobj/<sanitized-pkg>/<file>;.ddiplacement follows. Single-package builds keep the original layouttests/e2e/33_multi_version_mangling.sh— Y-shape: libA→cmdline 0.0.1, libB→cmdline 0.0.2; build succeeds with both BMIs on disktests/e2e/32_semver_merge.sh— irreconcilable case dropped (now handled by Level 1)MVP scope
Both limits surface as clear error messages with the workaround (pin one version explicitly). Recursive mangling for deeper graphs is a follow-up.
Test plan
tests/unit/test_mangle.cpp— 11 tests for name format + rewritertests/e2e/33_multi_version_mangling.sh(new)tests/e2e/32_semver_merge.sh(updated)tests/e2e/31_transitive_deps.shstill green