From 91f5745d339b0ce19bb2b424ba42e60235390ba5 Mon Sep 17 00:00:00 2001
From: "Jeffrey C. Ollie" <jeff@ocjtech.us>
Date: Thu, 10 Sep 2026 10:22:40 -0500
Subject: [PATCH] Compile everything without running it, with a check step

Three programs in this repository are reachable only from steps nobody runs in
the ordinary way: the benchmark from `bench`, the documentation server from
`docs-serve`, and the range generator from `update-ranges`. `zig build test`
builds none of them, so a change to the library that broke one would pass
every check the project had and be found by whoever next wanted a benchmark.

`zig build check` builds all three and runs nothing, and CI runs it on every
push. The generator is inside the lazy-dependency branch, so it is covered
once zxml has been fetched and skipped on a fresh clone rather than forcing
the fetch on everyone.

The workflow also gains `zig fmt --check .`, which the project has always been
expected to pass and nothing enforced, and it now runs the scalar tests first,
matching the default the previous commit set.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NJz47vhFE5XcSQUDbfP1N3
---
 .tangled/workflows/test.yml | 10 ++++++++--
 README.md                   |  8 ++++++++
 build.zig                   | 16 ++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/.tangled/workflows/test.yml b/.tangled/workflows/test.yml
index 106e62e..95f6df5 100644
--- a/.tangled/workflows/test.yml
+++ b/.tangled/workflows/test.yml
@@ -15,9 +15,15 @@ dependencies:
 steps:
   - name: "reuse lint"
     command: "reuse lint"
-  - name: "test (simd)"
-    command: "zig build test -Dsimd=true"
+  - name: "zig fmt"
+    command: "zig fmt --check ."
   - name: "test (scalar)"
     command: "zig build test -Dsimd=false"
+  - name: "test (simd)"
+    command: "zig build test -Dsimd=true"
+  # Everything `test` builds but never runs: the benchmark, the
+  # documentation server, and the range generator.
+  - name: "check"
+    command: "zig build check"
   - name: "docs"
     command: "zig build docs"
diff --git a/README.md b/README.md
index 225f956..cf389e0 100644
--- a/README.md
+++ b/README.md
@@ -115,6 +115,14 @@ zig build test
 
 The test suite includes unit tests and a fuzz test.
 
+`zig build check` compiles everything that `zig build test` does not
+run — the benchmark, the documentation server, and the range generator
+— so that none of them can quietly stop compiling.
+
+`zig build bench` compares the SIMD and scalar check digit
+implementations against each other; it calls both directly, so the
+`-Dsimd` setting does not affect what it measures.
+
 ## License
 
 [MIT](LICENSES/MIT.txt). This project is compliant with the
diff --git a/build.zig b/build.zig
index 0ace188..45505b9 100644
--- a/build.zig
+++ b/build.zig
@@ -36,6 +36,14 @@ pub fn build(b: *std.Build) void {
     const test_step = b.step("test", "Run tests");
     test_step.dependOn(&run_mod_tests.step);
 
+    // Everything that is built but not run by `zig build test`, gathered
+    // so that it cannot quietly stop compiling. The tools are reached only
+    // by steps nobody runs in the ordinary way -- the benchmark by `bench`,
+    // the documentation server by `docs-serve`, the range generator by
+    // `update-ranges` -- so without this a change to the library that broke
+    // one of them would pass CI.
+    const check_step = b.step("check", "Compile everything without running it");
+
     // The benchmark selects each implementation explicitly through
     // computeCheckDigitWith, so a single ReleaseFast module instance
     // covers both variants regardless of the -Dsimd setting.
@@ -64,6 +72,7 @@ pub fn build(b: *std.Build) void {
 
     const bench_step = b.step("bench", "Run benchmarks comparing SIMD and scalar check digit computation");
     bench_step.dependOn(&run_bench.step);
+    check_step.dependOn(&bench_exe.step);
 
     // -- documentation -------------------------------------------------------
     //
@@ -112,6 +121,8 @@ pub fn build(b: *std.Build) void {
     test_step.dependOn(&b.addRunArtifact(
         b.addTest(.{ .root_module = docs_server.root_module }),
     ).step);
+    check_step.dependOn(&docs_server.step);
+
     // The generator runs on the build host and writes into the source
     // tree, so it ignores -Dtarget and -Doptimize.
     const update_ranges_step = b.step("update-ranges", "Fetch the ISBN range data and regenerate src/ranges.zig");
@@ -141,5 +152,10 @@ pub fn build(b: *std.Build) void {
         const update_source = b.addUpdateSourceFiles();
         update_source.addCopyFileToSource(generated, "src/ranges.zig");
         update_ranges_step.dependOn(&update_source.step);
+
+        // Only reachable when zxml has already been fetched, so `zig build
+        // check` on a fresh clone covers everything else and picks this up
+        // the first time `update-ranges` is asked for.
+        check_step.dependOn(&generate_exe.step);
     }
 }
-- 
2.51.2