Allows compilation of code using debug.BuildInfo and show correct tinygo version (#4343)

debug: Allows compilation of code using debug.BuildInfo and show correct tinygo version

.gitignore

@@ -1,3 +1,5 @@
+.DS_Store
+.vscode
 go.work
 go.work.sum
 

src/runtime/debug/debug.go

@@ -1,6 +1,17 @@
-// Package debug is a dummy package that is not yet implemented.
+// Portions copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package debug is a very partially implemented package to allow compilation.
 package debug
 
+import (
+	"fmt"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
 // SetMaxStack sets the maximum amount of memory that can be used by a single
 // goroutine stack.
 //
@@ -27,16 +38,17 @@ func Stack() []byte {
 //
 // Not implemented.
 func ReadBuildInfo() (info *BuildInfo, ok bool) {
-	return nil, false
+	return &BuildInfo{GoVersion: runtime.Compiler + runtime.Version()}, true
 }
 
 // BuildInfo represents the build information read from
 // the running binary.
 type BuildInfo struct {
-	Path     string    // The main package path
-	Main     Module    // The module containing the main package
-	Deps     []*Module // Module dependencies
-	Settings []BuildSetting
+	GoVersion string    // version of the Go toolchain that built the binary, e.g. "go1.19.2"
+	Path      string    // The main package path
+	Main      Module    // The module containing the main package
+	Deps      []*Module // Module dependencies
+	Settings  []BuildSetting
 }
 
 type BuildSetting struct {
@@ -58,3 +70,60 @@ type Module struct {
 func SetGCPercent(n int) int {
 	return n
 }
+
+// Start of stolen from big go. TODO: import/reuse without copy pasta.
+
+// quoteKey reports whether key is required to be quoted.
+func quoteKey(key string) bool {
+	return len(key) == 0 || strings.ContainsAny(key, "= \t\r\n\"`")
+}
+
+// quoteValue reports whether value is required to be quoted.
+func quoteValue(value string) bool {
+	return strings.ContainsAny(value, " \t\r\n\"`")
+}
+
+func (bi *BuildInfo) String() string {
+	buf := new(strings.Builder)
+	if bi.GoVersion != "" {
+		fmt.Fprintf(buf, "go\t%s\n", bi.GoVersion)
+	}
+	if bi.Path != "" {
+		fmt.Fprintf(buf, "path\t%s\n", bi.Path)
+	}
+	var formatMod func(string, Module)
+	formatMod = func(word string, m Module) {
+		buf.WriteString(word)
+		buf.WriteByte('\t')
+		buf.WriteString(m.Path)
+		buf.WriteByte('\t')
+		buf.WriteString(m.Version)
+		if m.Replace == nil {
+			buf.WriteByte('\t')
+			buf.WriteString(m.Sum)
+		} else {
+			buf.WriteByte('\n')
+			formatMod("=>", *m.Replace)
+		}
+		buf.WriteByte('\n')
+	}
+	if bi.Main != (Module{}) {
+		formatMod("mod", bi.Main)
+	}
+	for _, dep := range bi.Deps {
+		formatMod("dep", *dep)
+	}
+	for _, s := range bi.Settings {
+		key := s.Key
+		if quoteKey(key) {
+			key = strconv.Quote(key)
+		}
+		value := s.Value
+		if quoteValue(value) {
+			value = strconv.Quote(value)
+		}
+		fmt.Fprintf(buf, "build\t%s=%s\n", key, value)
+	}
+
+	return buf.String()
+}