fix(build): a package's generated inputs come before its compiles; an empty link is refused (2026.8.30.1)

.github/actions/bootstrap-mcpp/action.yml

@@ -25,7 +25,7 @@ inputs:
     # `package.name`, so one of the two was simply unreachable — and which one
     # depended on the machine, which is why CI failed on `compat:lua` on
     # Windows and `mcpplibs.capi:lua` on Linux. Never pin below that.
-    default: '2026.8.27.5'
+    default: '2026.8.30.2'
   cache-target:
     description: also restore/save target/ (build artifacts + BMIs)
     required: false

.github/actions/setup-macos-llvm/action.yml

@@ -15,7 +15,7 @@ inputs:
     # Floor imposed by the index, not a routine bump — see
     # .github/actions/bootstrap-mcpp/action.yml for why 0.4.69 is required
     # (two packages named `lua` in one repo need openxlings/xlings#381).
-    default: '2026.8.27.5'
+    default: '2026.8.30.2'
 
 runs:
   using: composite

.github/workflows/bootstrap-macos.yml

@@ -17,7 +17,7 @@ jobs:
       # Dormant (workflow_dispatch only), but kept in step with the rest —
       # check_version_pins.sh holds it there. Floor: 0.4.69, below which the
       # index cannot resolve two packages that share a short name.
-      XLINGS_VERSION: '2026.8.27.5'
+      XLINGS_VERSION: '2026.8.30.2'
     steps:
       - uses: actions/checkout@v4
 

.github/workflows/ci-fresh-install.yml

@@ -152,7 +152,7 @@ jobs:
         env:
           XLINGS_NON_INTERACTIVE: '1'
         run: |
-          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.27.5
+          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.30.2
           echo "$HOME/.xlings/subos/current/bin" >> "$GITHUB_PATH"
 
       - name: Install mcpp and config mirror
@@ -293,7 +293,7 @@ jobs:
 
       - name: Install xlings + mcpp
         run: |
-          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.27.5
+          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.30.2
           # Deliberately NOT writing to $GITHUB_PATH here. On container
           # images that declare no PATH in their config (opensuse/
           # tumbleweed), appending a single dir to GITHUB_PATH makes the
@@ -364,7 +364,7 @@ jobs:
           #             (older ones carry minos=15 and refuse to start).
           #   v0.4.51+: in-process sha256 — this image has no sha256sum
           #             binary, so pinned fetches failed before it.
-          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.27.5
+          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.30.2
           echo "$HOME/.xlings/subos/current/bin" >> "$GITHUB_PATH"
 
       - name: Install mcpp and config mirror

.github/workflows/ci-linux-e2e.yml

@@ -237,7 +237,7 @@ jobs:
 
       - name: Bootstrap xlings + released mcpp
         run: |
-          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.27.5
+          curl -fsSL https://raw.githubusercontent.com/openxlings/xlings/main/tools/other/quick_install.sh | bash -s v2026.8.30.2
           export PATH="$HOME/.xlings/subos/current/bin:$PATH"
           xlings update
           xlings install mcpp -y -g

.github/workflows/cross-build-test.yml

@@ -122,7 +122,7 @@ jobs:
           # release assets were uploaded in a broken state (records present,
           # blobs missing → 404 on GET); re-uploaded clean. The stale-INDEX
           # half is handled by the marker-clear below.
-          XLINGS_VERSION: '2026.8.27.5'
+          XLINGS_VERSION: '2026.8.30.2'
         run: |
           tarball="xlings-${XLINGS_VERSION}-linux-x86_64.tar.gz"
           bash "$GITHUB_WORKSPACE/.github/tools/fetch_release.sh" \
@@ -263,7 +263,7 @@ jobs:
       - name: Bootstrap mcpp via xlings
         env:
           XLINGS_NON_INTERACTIVE: '1'
-          XLINGS_VERSION: '2026.8.27.5'
+          XLINGS_VERSION: '2026.8.30.2'
         run: |
           tarball="xlings-${XLINGS_VERSION}-linux-x86_64.tar.gz"
           bash "$GITHUB_WORKSPACE/.github/tools/fetch_release.sh" \

.github/workflows/release.yml

@@ -96,7 +96,7 @@ jobs:
           # Pin xlings to a known-good version. The upstream install
           # script always grabs `latest` (no version override), so we
           # download + self-install manually to avoid broken releases.
-          XLINGS_VERSION: '2026.8.27.5'
+          XLINGS_VERSION: '2026.8.30.2'
         run: |
           if [ ! -x "$HOME/.xlings/subos/default/bin/xlings" ]; then
             tarball="xlings-${XLINGS_VERSION}-linux-x86_64.tar.gz"
@@ -289,7 +289,7 @@ jobs:
       - name: Bootstrap mcpp via xlings
         env:
           XLINGS_NON_INTERACTIVE: '1'
-          XLINGS_VERSION: '2026.8.27.5'
+          XLINGS_VERSION: '2026.8.30.2'
         run: |
           tarball="xlings-${XLINGS_VERSION}-linux-x86_64.tar.gz"
           bash "$GITHUB_WORKSPACE/.github/tools/fetch_release.sh" \
@@ -360,7 +360,7 @@ jobs:
           # below are pinned to the same version as XLINGS_VERSION; they are
           # NOT interpolated from it, so check_version_pins.sh scans for them
           # explicitly (they were absent from the old lock-step comment).
-          XLA="xlings-2026.8.27.5-linux-aarch64.tar.gz"
+          XLA="xlings-2026.8.30.2-linux-aarch64.tar.gz"
           # NOT fetch_release.sh: this asset is OPTIONAL and the `if` is the
           # point — an arch with no prebuilt xlings must fall through quietly,
           # while the helper retries a 404 five times before giving up. The one
@@ -369,9 +369,9 @@ jobs:
           # cover it.
           if curl -fsSL --retry 3 --retry-delay 2 --retry-all-errors \
                --connect-timeout 20 --max-time 600 -o "/tmp/$XLA" \
-               "https://github.com/openxlings/xlings/releases/download/v2026.8.27.5/$XLA"; then
+               "https://github.com/openxlings/xlings/releases/download/v2026.8.30.2/$XLA"; then
             tar -xzf "/tmp/$XLA" -C /tmp
-            XLBIN=$(find /tmp/xlings-2026.8.27.5-linux-aarch64 -path '*/bin/xlings' -type f | head -1)
+            XLBIN=$(find /tmp/xlings-2026.8.30.2-linux-aarch64 -path '*/bin/xlings' -type f | head -1)
             if [ -n "$XLBIN" ]; then
               mkdir -p "$STAGING/$WRAPPER/registry/bin"
               cp "$XLBIN" "$STAGING/$WRAPPER/registry/bin/xlings"
@@ -449,7 +449,7 @@ jobs:
       - name: Bootstrap mcpp via xlings
         env:
           XLINGS_NON_INTERACTIVE: '1'
-          XLINGS_VERSION: '2026.8.27.5'
+          XLINGS_VERSION: '2026.8.30.2'
         run: |
           if [ ! -x "$HOME/.xlings/subos/default/bin/xlings" ]; then
             WORK=$(mktemp -d)
@@ -632,7 +632,7 @@ jobs:
         shell: bash
         env:
           XLINGS_NON_INTERACTIVE: '1'
-          XLINGS_VERSION: '2026.8.27.5'
+          XLINGS_VERSION: '2026.8.30.2'
         run: |
           # Captured before the `cd` below, in POSIX form: this step never
           # returns to the workspace, and GITHUB_WORKSPACE is a backslash

docs/07-build-mcpp.md

@@ -311,14 +311,27 @@ attach:
 
 | `role` | Outputs | Ordering | Typical |
 |---|---|---|---|
-| `source` | join the compile set | the compile edge consumes them | protoc, a transpiler |
-| `check` | a stamp file, written by mcpp | runs **alongside** compilation (set `blocking = true` to gate it) | clang-tidy, a format or ABI check |
+| `source` | compilable ones join the compile set; the rest are produced but not compiled | **every compile edge of the declaring package waits for them** | protoc, a transpiler, a protocol/IDL generator |
+| `check` | a stamp file, written by mcpp | runs **alongside** compilation; `blocking = true` makes the package's compile edges wait for it | clang-tidy, a format or ABI check |
 | `object` | join the **link** set | the link edge consumes them | a resource compiler, `objcopy` embedding a blob, a generated `.def`, a pre-built `.o` |
 | `artifact` | a new file | its *inputs* are link outputs, so it runs after the link | codesign, packaging, size budgets |
 
-No phase machinery is involved: ninja's own file dependencies do the
-sequencing, which is also why an `artifact` action cannot double-apply itself
-the way a naive "post-build hook" would.
+No phase machinery is involved. `object` and `artifact` are sequenced by
+ninja's own file dependencies — which is also why an `artifact` action cannot
+double-apply itself the way a naive "post-build hook" would. `source` and a
+blocking `check` are sequenced by an order-only edge from the declaring
+package's compile edges to that package's action outputs.
+
+> **Why `source` needs the edge (mcpp 2026.8.30.2+).** A generated `.cpp`
+> becomes an input of the edge that compiles it, so it was ordered for free. A
+> generated **header** never does: it is reached through `-I`, and the depfile
+> that would record it does not exist until a compile has already succeeded.
+> Before this, an action whose outputs were all headers had a node in
+> `build.ninja` that nothing could reach — not `default`, not the goal set, no
+> consuming edge — so it never ran, and what the compiler read was the empty
+> placeholder mcpp writes for a declared output. The ordering is **per
+> package**, because `include_dir` colours only the declaring package's own
+> translation units.
 
 **A check's command does not have to write its stamp** (mcpp 2026.8.29.1+).
 The verdict is the exit code; the stamp is bookkeeping the graph needs, and

docs/zh/07-build-mcpp.md

@@ -277,13 +277,22 @@ int main() {
 
 | `role` | 输出 | 顺序 | 典型 |
 |---|---|---|---|
-| `source` | 进编译集 | 编译边消费它们 | protoc、转译器 |
-| `check` | 一个 stamp 文件,由 mcpp 写入 | **与编译并行**(`blocking = true` 才前置) | clang-tidy、格式/ABI 检查 |
+| `source` | 可编译的进编译集,其余只产出、不编译 | **声明它的那个包的每条编译边都等它** | protoc、转译器、协议/IDL 生成器 |
+| `check` | 一个 stamp 文件,由 mcpp 写入 | 与编译并行;`blocking = true` 让该包的编译边等它 | clang-tidy、格式/ABI 检查 |
 | `object` | 进**链接**集 | 链接边消费它们 | 资源编译器、`objcopy` 嵌 blob、生成的 `.def`、预编译 `.o` |
 | `artifact` | 一个新文件 | 它的**输入**是链接产物,所以在链接之后跑 | 签名、打包、size budget |
 
-全程不涉及任何 phase 机制:顺序由 ninja 自己的文件依赖决定 —— 这也是为什么
-`artifact` 不会像朴素的「post 构建钩子」那样把自己重复施加一遍。
+全程不涉及任何 phase 机制。`object` 与 `artifact` 由 ninja 自己的文件依赖定序 ——
+这也是为什么 `artifact` 不会像朴素的「post 构建钩子」那样把自己重复施加一遍。
+`source` 与 blocking 的 `check` 则由一条 order-only 边定序:从声明它的那个包的
+编译边,指向该包的 action 产物。
+
+> **`source` 为什么需要这条边(mcpp 2026.8.30.2+)。** 生成的 `.cpp` 会成为编译它
+> 那条边的输入,所以顺序是白得的。生成的**头文件**永远不会:它是通过 `-I` 找到的,
+> 而能记录它的 depfile 要等到某次编译成功之后才存在。在此之前,一个产物全是头文件的
+> action 在 `build.ninja` 里有节点却无人可达 —— 不在 `default`、不在 goal 集、没有
+> 任何边消费它 —— 于是它从不执行,而编译器读到的是 mcpp 为已声明产物写下的那个空占位
+> 文件。这条边**按包**划分,因为 `include_dir` 只染色声明它的那个包自己的 TU。
 
 **check 的命令不必自己写 stamp**(mcpp 2026.8.29.1+)。判定是退出码,stamp 是**构建图**
 需要的记账;命令成功时由 mcpp 创建它。在此之前每个 check 都需要一个包装脚本去 touch

mcpp.toml

@@ -1,6 +1,6 @@
 [package]
 name        = "mcpp"
-version = "2026.8.29.1"
+version = "2026.8.30.1"
 description = "Modern C++ build & package management tool"
 license     = "Apache-2.0"
 authors     = ["mcpp-community"]

modules/buildmcpp/src/directives.cppm

@@ -387,8 +387,17 @@ std::string action_error(const Directives& d);
 // Never truncates an existing file: after the first build the real content is
 // there, and rewriting it would make ninja think the input changed on every
 // prepare.
+//
+// ⚠️ ONLY FOR OUTPUTS THAT ARE TRANSLATION UNITS, which is why this needs the
+// table. A placeholder exists so the SCAN has something to read, and the scan
+// never reads a header — but writing one anyway turned "the generator did not
+// run" into "the header is empty", and mcpp#534 was diagnosed as a race for
+// exactly that reason: the file was on disk, so the action looked like it had
+// run. A missing file is the honest report, and after the ordering fix the
+// generator runs before anything reads it either way.
 void prepare_actions(std::vector<mcpp::manifest::BuildAction>& actions,
-                     const std::filesystem::path& pkgRoot);
+                     const std::filesystem::path& pkgRoot,
+                     const mcpp::ExtensionTable& extensions);
 
 // Does this action output belong in the COMPILE set?
 //
@@ -773,7 +782,8 @@ bool is_compilable_output(const fs::path& p, const mcpp::ExtensionTable& t) {
 }
 
 void prepare_actions(std::vector<mcpp::manifest::BuildAction>& actions,
-                     const fs::path& pkgRoot) {
+                     const fs::path& pkgRoot,
+                     const mcpp::ExtensionTable& extensions) {
     for (auto& a : actions) {
         auto absolutize = [&](std::vector<std::string>& v) {
             for (auto& p : v) {
@@ -788,6 +798,11 @@ void prepare_actions(std::vector<mcpp::manifest::BuildAction>& actions,
         if (a.role != mcpp::manifest::BuildAction::Role::Source) continue;
         for (auto const& o : a.outputs) {
             if (o.find("${mcpp.") != std::string::npos) continue;
+            // A placeholder exists so the scan has a translation unit to read.
+            // A header is not one — nothing scans it, and the empty file it
+            // used to leave behind is what made a generator that never ran
+            // look like one that had (mcpp#534).
+            if (!is_compilable_output(o, extensions)) continue;
             std::error_code ec;
             fs::path p(o);
             if (fs::exists(p, ec)) continue;      // real content already there

modules/manifest/src/types.cppm

@@ -300,6 +300,18 @@ struct BuildAction {
     enum class Role { Source, Check, Object, Artifact };
 
     std::string                        id;        // diagnostics + edge naming
+    // Which package's `build.mcpp` declared this. Filled by the engine when
+    // actions are collected into the plan, NOT by the build program — the
+    // program does not know, and the engine already does.
+    //
+    // Load-bearing, not bookkeeping: the ordering edge an action needs is
+    // scoped to the declaring package, because `include_dir` colours only that
+    // package's own translation units. A build-wide ordering would express a
+    // dependency that does not exist and put it on the critical path of a
+    // build whose wall clock is dominated by one. Spelled the same way
+    // `CompileUnit::packageName` is (`qualified_package_name`), because the
+    // two are matched against each other.
+    std::string                        packageName;
     Role                               role = Role::Source;
     std::vector<std::string>           inputs;    // absolute or package-relative
     std::vector<std::string>           outputs;   // ditto; declared, see INV-D

modules/versioning/src/version.cppm

@@ -31,6 +31,6 @@ import std;
 
 export namespace mcpp {
 
-inline constexpr std::string_view MCPP_VERSION = "2026.8.29.1";
+inline constexpr std::string_view MCPP_VERSION = "2026.8.30.1";
 
 } // namespace mcpp