rename packages, refactor out tailwind compiler,

go/cmd/examples/go-wasm-web/buildsteps/buildsteps.go

@@ -0,0 +1,106 @@
+// Package buildsteps is the example's build pipeline: directive codegen, Tailwind,
+// the wasm binary, and Go's JS shim.
+//
+// It is Go, not a shell script, for three reasons. The dev server needs to call these
+// steps on every save and cannot shell out to bash on Windows. Editors need to run
+// them as tasks, and a task that only works on one platform is a task half the team
+// cannot use. And the one-off build and the watch build must be the SAME steps — the
+// moment they are two scripts, they drift, and the bug only shows up in whichever one
+// you use less.
+//
+// Run the whole thing with `go run ./build`.
+package buildsteps
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+// kjolRoot is the kjol Go module root, relative to the example directory. The Tailwind
+// and codegen commands are run FROM there so the engine's dependencies resolve in
+// kjol's own go.mod, and this example's stays lean.
+const kjolRoot = "../../.."
+
+// Wwwroot is where every build artefact lands, and what the dev server serves.
+const Wwwroot = "wwwroot"
+
+// Codegen regenerates app/*.gen.go from the //gowasm: directives — the routes, the
+// layouts, and the client stubs for server components. It runs FIRST: everything after
+// it compiles the code it writes.
+func Codegen() ([]byte, error) {
+	return run("go", "run", "kjol/cmd/wasmgen", "./app")
+}
+
+// Tailwind compiles css/app.css to wwwroot/app.css, scanning the webui kit and this
+// example's Go markup for utility candidates.
+//
+// It scans .go files, which is the whole point of kjol's native engine: the markup is
+// written in Go, so that is where the class names are. There is no JS build here at
+// all.
+func Tailwind() ([]byte, error) {
+	cmd := exec.Command("go", "run", "./cmd/twcss",
+		"-entry", "cmd/examples/go-wasm-web/css/app.css",
+		"-out", "cmd/examples/go-wasm-web/wwwroot/app.css",
+		"-base", ".",
+		"webui/**/*.go",
+		"cmd/examples/go-wasm-web/app/**/*.go",
+		"cmd/examples/go-wasm-web/server/**/*.go",
+	)
+	cmd.Dir = kjolRoot
+	return cmd.CombinedOutput()
+}
+
+// Wasm compiles ./wasm to wwwroot/app.wasm.
+func Wasm() ([]byte, error) {
+	cmd := exec.Command("go", "build", "-o", filepath.Join(Wwwroot, "app.wasm"), "./wasm")
+	cmd.Env = append(os.Environ(), "GOOS=js", "GOARCH=wasm")
+	return cmd.CombinedOutput()
+}
+
+// Shim copies Go's wasm_exec.js into wwwroot. It is the loader the browser needs to
+// start a Go wasm binary, it ships with the toolchain, and it must match the compiler
+// that produced the binary — so it is copied from GOROOT rather than vendored.
+func Shim() ([]byte, error) {
+	out, err := exec.Command("go", "env", "GOROOT").Output()
+	if err != nil {
+		return out, err
+	}
+	goroot := strings.TrimSpace(string(out))
+
+	for _, src := range []string{
+		filepath.Join(goroot, "lib", "wasm", "wasm_exec.js"),  // Go >= 1.24
+		filepath.Join(goroot, "misc", "wasm", "wasm_exec.js"), // Go <= 1.23
+	} {
+		b, err := os.ReadFile(src)
+		if err != nil {
+			continue
+		}
+		dst := filepath.Join(Wwwroot, "wasm_exec.js")
+		// The GOROOT copy is read-only, and so is the copy we made last time. Remove it
+		// first, or the write fails with a permission error that says nothing useful.
+		os.Remove(dst)
+		return nil, os.WriteFile(dst, b, 0o644)
+	}
+	return nil, os.ErrNotExist
+}
+
+// All is the full build, in order. It is what the dev server runs on a code change and
+// what `go run ./build` runs once.
+//
+// Returned output is the failing command's combined stdout+stderr, which the dev server
+// puts straight into the browser's error overlay — so a compile error lands in front of
+// you rather than in a terminal you were not looking at.
+func All() ([]byte, error) {
+	for _, step := range []func() ([]byte, error){Codegen, Tailwind, Wasm, Shim} {
+		if out, err := step(); err != nil {
+			return out, err
+		}
+	}
+	return nil, nil
+}
+
+func run(name string, args ...string) ([]byte, error) {
+	return exec.Command(name, args...).CombinedOutput()
+}