From b6db84e916925b76251ad4aacef39f01a3baa57a Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sat, 29 Sep 2018 22:30:45 +0200
Subject: [PATCH] main: use GOPATH from the environment

Be more compatible with the Go toolchain by setting GOPATH in the same
way. This makes it possible to flash and run examples from the standard
GOPATH instead of only from the source tree.
---
 compiler/compiler.go | 12 +++++++++++-
 main.go              |  2 ++
 target.go            | 21 +++++++++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/compiler/compiler.go b/compiler/compiler.go
index 0da00b40..a6355cb2 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -34,6 +34,7 @@ type Config struct {
 	DumpSSA   bool     // dump Go SSA, for compiler debugging
 	Debug     bool     // add debug symbols for gdb
 	RootDir   string   // GOROOT for TinyGo
+	GOPATH    string   // GOPATH, like `go env GOPATH`
 	BuildTags []string // build tags for TinyGo (empty means {runtime.GOOS/runtime.GOARCH})
 }
 
@@ -151,6 +152,15 @@ func (c *Compiler) Module() llvm.Module {
 func (c *Compiler) Compile(mainPath string) error {
 	tripleSplit := strings.Split(c.Triple, "-")
 
+	// Prefix the GOPATH with the system GOROOT, as GOROOT is already set to
+	// the TinyGo root.
+	gopath := c.GOPATH
+	if gopath == "" {
+		gopath = runtime.GOROOT()
+	} else {
+		gopath = runtime.GOROOT() + string(filepath.ListSeparator) + gopath
+	}
+
 	config := loader.Config{
 		TypeChecker: types.Config{
 			Sizes: &StdSizes{
@@ -163,7 +173,7 @@ func (c *Compiler) Compile(mainPath string) error {
 			GOARCH:      tripleSplit[0],
 			GOOS:        tripleSplit[2],
 			GOROOT:      c.RootDir,
-			GOPATH:      runtime.GOROOT(),
+			GOPATH:      gopath,
 			CgoEnabled:  true,
 			UseAllFiles: false,
 			Compiler:    "gc", // must be one of the recognized compilers
diff --git a/main.go b/main.go
index 43f09f7a..9137bc3f 100644
--- a/main.go
+++ b/main.go
@@ -22,6 +22,7 @@ func Compile(pkgName, outpath string, spec *TargetSpec, printIR, dumpSSA, debug
 		Debug:     debug,
 		DumpSSA:   dumpSSA,
 		RootDir:   sourceDir(),
+		GOPATH:    getGopath(),
 		BuildTags: spec.BuildTags,
 	}
 	c, err := compiler.NewCompiler(pkgName, config)
@@ -198,6 +199,7 @@ func Flash(pkgName, target, port string, printIR, dumpSSA, debug bool, printSize
 func Run(pkgName string) error {
 	config := compiler.Config{
 		RootDir: sourceDir(),
+		GOPATH:  getGopath(),
 	}
 	c, err := compiler.NewCompiler(pkgName, config)
 	if err != nil {
diff --git a/target.go b/target.go
index 43a9700d..8f7a44cc 100644
--- a/target.go
+++ b/target.go
@@ -58,3 +58,24 @@ func sourceDir() string {
 	_, path, _, _ := runtime.Caller(0)
 	return filepath.Dir(path)
 }
+
+func getGopath() string {
+	gopath := os.Getenv("GOPATH")
+	if gopath != "" {
+		return gopath
+	}
+
+	// fallback
+	var home string
+	if runtime.GOOS == "windows" {
+		home = os.Getenv("USERPROFILE")
+	} else {
+		home = os.Getenv("HOME")
+	}
+	if home == "" {
+		// This is very unlikely, so panic here.
+		// Not the nicest solution, however.
+		panic("no $HOME or %USERPROFILE% found")
+	}
+	return filepath.Join(home, "go")
+}