From 6f63e574a9016281a12c1318c6726af43e45d3df Mon Sep 17 00:00:00 2001
From: Nick Galbreath <nickg@signalsciences.com>
Date: Mon, 26 Oct 2015 15:01:06 -0700
Subject: [PATCH] add context object

---
 golist/packages.go      | 65 +++++++++++++++++++++++++++++++++++++++++
 golist/packages_test.go | 12 +++++++-
 2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/golist/packages.go b/golist/packages.go
index 10a0aca..7890603 100644
--- a/golist/packages.go
+++ b/golist/packages.go
@@ -3,14 +3,31 @@ package golist
 import (
 	"bufio"
 	"encoding/json"
+	"fmt"
 	"io"
 	//	"fmt"
 	"log"
 	"os"
 	"os/exec"
 	"sort"
+	"strings"
 )
 
+// Context is similar to
+// // https://github.com/golang/go/blob/master/src/cmd/go/context.go
+type Context struct {
+	GOARCH        string   // target architecture
+	GOOS          string   // target operating system
+	GOROOT        string   // Go root
+	GOPATH        string   // Go path
+	CgoEnabled    bool     // whether cgo can be used
+	UseAllFiles   bool     // use files regardless of +build lines, file names
+	Compiler      string   // compiler to assume when computing target paths
+	BuildTags     []string // build constraints to match in +build lines
+	ReleaseTags   []string // releases the current release is compatible with
+	InstallSuffix string   // suffix to use in the name of the install dir
+}
+
 // A PackageError describes an error loading information about a package.
 type PackageError struct {
 	ImportStack []string // shortest path from package named on command line to this one
@@ -177,3 +194,51 @@ func Deps(name ...string) ([]string, error) {
 	sort.Strings(paths)
 	return paths, nil
 }
+
+/*
+fm := template.FuncMap{
+	"join":    strings.Join,
+	"context": context,
+}
+*/
+
+const contextTemplate = `{{ with context }}{{ .GOARCH }}
+{{ .GOOS }}
+{{ .GOROOT }}
+{{ .GOPATH }}
+{{ .CgoEnabled }}
+{{ .UseAllFiles }}
+{{ .Compiler }}
+{{ join .BuildTags "," }}
+{{ join .ReleaseTags "," }}
+{{ .InstallSuffix }}{{ end }}`
+
+// NewContext generates a context object
+func NewContext() (*Context, error) {
+	c := Context{}
+	cmd := exec.Command("go", "list", "-f", contextTemplate)
+	outbytes, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+	lines := strings.Split(string(outbytes), "\n")
+	if len(lines) != 10 {
+		return nil, fmt.Errorf("expected 10 outlines from golist, got %d with %q", len(lines), string(outbytes))
+	}
+	c.GOARCH = lines[0]
+	c.GOOS = lines[1]
+	c.GOROOT = lines[2]
+	c.GOPATH = lines[3]
+	if lines[4] == "true" {
+		c.CgoEnabled = true
+	}
+	if lines[5] == "true" {
+		c.UseAllFiles = true
+	}
+	c.Compiler = lines[6]
+	c.BuildTags = strings.Split(lines[7], ",")
+	c.ReleaseTags = strings.Split(lines[8], ",")
+	c.InstallSuffix = lines[9]
+
+	return &c, nil
+}
diff --git a/golist/packages_test.go b/golist/packages_test.go
index 55d902b..b0fc594 100644
--- a/golist/packages_test.go
+++ b/golist/packages_test.go
@@ -8,7 +8,7 @@ import (
 // TestGoListStd tests GoListStd.  This is really over kill
 //  for the current implimentation, but previous one was much weirder
 func TestGoListStd(t *testing.T) {
-	pkgs, err := GoListStd()
+	pkgs, err := Std()
 	if err != nil {
 		t.Fatalf("Unable to get standard packages: %s", err)
 	}
@@ -43,3 +43,13 @@ func TestGoListStd(t *testing.T) {
 		}
 	}
 }
+
+func TestNewContext(t *testing.T) {
+	c, err := NewContext()
+	if err != nil {
+		t.Fatalf("Unable to get context: %s", err)
+	}
+	if c.GOARCH != "amd64" {
+		t.Errorf("GOARCH not set correctly: %q", c.GOARCH)
+	}
+}