tests: a capture is a delta and a click names its word, so a tagline edit stops rewriting the suite

1 files changed, 21 insertions, 3 deletions

diff --git a/build.zig b/build.zig
index 7d380eb8..061d1f2c 100644
--- a/build.zig
+++ b/build.zig
@@ -76,6 +76,12 @@ pub fn build(b: *std.Build) void {
     const requested_optimize = b.standardOptimizeOption(.{});
     const static = b.option(bool, "static", "statically link") orelse false;
     const dump_path = b.option([]const u8, "dump", "dump .zon embedded into the web shell (-Dplatform=web)");
+    // one substring, because that is what a dev loop needs: see the unit-test
+    // step for why the whole-binary run is worth narrowing
+    const test_filters: []const []const u8 = if (b.option([]const u8, "test-filter", "run only tests whose name contains this")) |f|
+        &.{f}
+    else
+        &.{};
     const is_web = platform == .web;
     const enable_mupdf = b.option(bool, "mupdf", "native PDF rendering with MuPDF (AGPL/commercial; native default on, web off; -Dmupdf=false disables)") orelse !is_web;
     // JPEG 2000, and with it scanned PDFs: a scan is one /JPXDecode image per
@@ -243,7 +249,12 @@ pub fn build(b: *std.Build) void {
         .name = "pardes-gen-themes",
         .root_module = b.createModule(.{
             .target = b.graph.host,
-            .optimize = .ReleaseSafe,
+            // Debug on purpose: it runs for ~40ms, and every core module
+            // imports what it generates, so its compile is the first link of
+            // every cold build. ReleaseSafe cost 16s of compile to save 47ms of
+            // run time, and the 226 files it writes are byte-identical either
+            // way.
+            .optimize = .Debug,
             .root_source_file = b.path("tools/gen_themes.zig"),
         }),
     });
@@ -1025,7 +1036,7 @@ pub fn build(b: *std.Build) void {
         // configuration theirs is not declared. macos.zig imports the core, so
         // this one aggregate reaches both the C-ABI guard and the core tests.
         const unit_step = b.step("unit-test", "run the C-ABI guard and core unit tests");
-        unit_step.dependOn(&b.addRunArtifact(b.addTest(.{ .root_module = root_mod })).step);
+        unit_step.dependOn(&b.addRunArtifact(b.addTest(.{ .root_module = root_mod, .filters = test_filters })).step);
         web_step.dependOn(&b.addFail("web needs -Dplatform=web -Dtarget=wasm32-freestanding -Ddump=<dump.zon>").step);
     } else {
         // binary name: the native-shaped linux-x86_64 tty build stays `pardes`
@@ -1295,8 +1306,15 @@ pub fn build(b: *std.Build) void {
         // runtime switch, which test analysis never enters. main.zig's test
         // block names the selected shell, user config, and platform-only
         // helpers; its ordinary core import reaches pardes.zig and modal.zig.
+        //
+        // `-Dtest-filter=<substring>` narrows it. The whole binary is 14s and
+        // two tests are 8.6s of that, so a one-line change to a module with a
+        // three-millisecond test used to cost the full run: `zig build
+        // unit-test -Dtest-filter="an untouched tagline"` is ~1s. The test
+        // runner's own `--test-filter` never worked here - nothing forwarded
+        // `--` args to the run step, so it was parsed as a script name.
         if (platform == .tty or platform == .gui) {
-            const shell_test = b.addTest(.{ .root_module = root_mod });
+            const shell_test = b.addTest(.{ .root_module = root_mod, .filters = test_filters });
             unit_step.dependOn(&b.addRunArtifact(shell_test).step);
         }
     }