goose: dependency injection proof of concept

See documentation and demo for usage and known limitations.

Reviewed-by: Herbie Ong <herbie@google.com>

main.go

@@ -0,0 +1,52 @@
+// goose is a compile-time dependency injection tool.
+//
+// See README.md for an overview.
+package main
+
+import (
+	"fmt"
+	"go/build"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"codename/goose/internal/goose"
+)
+
+func main() {
+	var pkg string
+	switch len(os.Args) {
+	case 1:
+		pkg = "."
+	case 2:
+		pkg = os.Args[1]
+	default:
+		fmt.Fprintln(os.Stderr, "goose: usage: goose [PKG]")
+		os.Exit(64)
+	}
+	wd, err := os.Getwd()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "goose:", err)
+		os.Exit(1)
+	}
+	pkgInfo, err := build.Default.Import(pkg, wd, build.FindOnly)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "goose:", err)
+		os.Exit(1)
+	}
+	out, err := goose.Generate(&build.Default, wd, pkg)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "goose:", err)
+		os.Exit(1)
+	}
+	if len(out) == 0 {
+		// No Goose directives, don't write anything.
+		fmt.Fprintln(os.Stderr, "goose: no injector found for", pkg)
+		return
+	}
+	p := filepath.Join(pkgInfo.Dir, "goose_gen.go")
+	if err := ioutil.WriteFile(p, out, 0666); err != nil {
+		fmt.Fprintln(os.Stderr, "goose:", err)
+		os.Exit(1)
+	}
+}