cmd/go: move module build info formatting into runtime/debug

Previously, modload.PackageBuildInfo returned a string containing
information about modules used to build an executable. This string is
embedded in the binary and can be read with debug.ReadBuildInfo or
'go version -m'.

With this change, debug.BuildInfo now has a MarshalText method that
returns a string in the same format as modload.PackageBuildInfo.

Package.load now calls Package.setBuildInfo, which constructs a
debug.BuildInfo, formats it with MarshalText, then sets
Package.Internal.BuildInfo. This is equivalent to what
modload.PackageBuildInfo did.

modload.PackageBuildInfo is deleted, since it's no longer used.

For #37475

Change-Id: I5875a98cb64737637fec2a450ab2ffa7f1805707
Reviewed-on: https://go-review.googlesource.com/c/go/+/353886
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/runtime/debug/mod.go b/src/runtime/debug/mod.go
index 05cad61155..11f995ba75 100644
--- a/src/runtime/debug/mod.go
+++ b/src/runtime/debug/mod.go
@@ -5,6 +5,8 @@
 package debug
 
 import (
+	"bytes"
+	"fmt"
 	"strings"
 )
 
@@ -34,6 +36,41 @@ type Module struct {
 	Replace *Module // replaced by this module
 }
 
+func (bi *BuildInfo) MarshalText() ([]byte, error) {
+	buf := &bytes.Buffer{}
+	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)
+		mv := m.Version
+		if mv == "" {
+			mv = "(devel)"
+		}
+		buf.WriteByte('\t')
+		buf.WriteString(mv)
+		if m.Replace == nil {
+			buf.WriteByte('\t')
+			buf.WriteString(m.Sum)
+		} else {
+			buf.WriteByte('\n')
+			formatMod("=>", *m.Replace)
+		}
+		buf.WriteByte('\n')
+	}
+	if bi.Main.Path != "" {
+		formatMod("mod", bi.Main)
+	}
+	for _, dep := range bi.Deps {
+		formatMod("dep", *dep)
+	}
+
+	return buf.Bytes(), nil
+}
+
 func readBuildInfo(data string) (*BuildInfo, bool) {
 	if len(data) < 32 {
 		return nil, false