os: remove Getenverror

Fixes #3065

R=golang-dev, dsymonds, rsc
CC=golang-dev
https://golang.org/cl/5675094

doc/go1.html

@@ -1451,7 +1451,14 @@ with more Go-like names, such as
 <a href="/pkg/os/#ErrPermission"><code>ErrPermission</code></a>
 and
 <a href="/pkg/os/#ErrNoEnv"><code>ErrNoEnv</code></a>.
+</p>
 
+<p>
+The <code>Getenverror</code> function has been removed. To distinguish
+between a non-existent environment variable and an empty string,
+use <a href="/pkg/os/#Environ"><code>os.Environ</code></a> or
+<a href="/pkg/syscall/#Getenv"><code>syscall.Getenv</code></a>.
+</p>
 
 <p>
 <em>Updating</em>:

doc/go1.tmpl

@@ -1354,7 +1354,14 @@ with more Go-like names, such as
 <a href="/pkg/os/#ErrPermission"><code>ErrPermission</code></a>
 and
 <a href="/pkg/os/#ErrNoEnv"><code>ErrNoEnv</code></a>.
+</p>
 
+<p>
+The <code>Getenverror</code> function has been removed. To distinguish
+between a non-existent environment variable and an empty string,
+use <a href="/pkg/os/#Environ"><code>os.Environ</code></a> or
+<a href="/pkg/syscall/#Getenv"><code>syscall.Getenv</code></a>.
+</p>
 
 <p>
 <em>Updating</em>:

misc/dashboard/builder/main.go

@@ -480,8 +480,7 @@ func (b *Builder) envv() []string {
 		"GOROOT_FINAL=/usr/local/go",
 	}
 	for _, k := range extraEnv {
-		s, err := os.Getenverror(k)
-		if err == nil {
+		if s, ok := getenvOk(k); ok {
 			e = append(e, k+"="+s)
 		}
 	}
@@ -497,8 +496,7 @@ func (b *Builder) envvWindows() []string {
 		"GOBUILDEXIT":  "1", // exit all.bat with completion status.
 	}
 	for _, name := range extraEnv {
-		s, err := os.Getenverror(name)
-		if err == nil {
+		if s, ok := getenvOk(name); ok {
 			start[name] = s
 		}
 	}
@@ -782,3 +780,17 @@ func defaultSuffix() string {
 	}
 	return ".bash"
 }
+
+func getenvOk(k string) (v string, ok bool) {
+	v = os.Getenv(k)
+	if v != "" {
+		return v, true
+	}
+	keq := k + "="
+	for _, kv := range os.Environ() {
+		if kv == keq {
+			return "", true
+		}
+	}
+	return "", false
+}

src/pkg/os/env.go

@@ -6,10 +6,7 @@
 
 package os
 
-import (
-	"errors"
-	"syscall"
-)
+import "syscall"
 
 // Expand replaces ${var} or $var in the string based on the mapping function.
 // Invocations of undefined variables are replaced with the empty string.
@@ -77,26 +74,10 @@ func getShellName(s string) (string, int) {
 	return s[:i], i
 }
 
-// ENOENV is the error indicating that an environment variable does not exist.
-var ENOENV = errors.New("no such environment variable")
-
-// Getenverror retrieves the value of the environment variable named by the key.
-// It returns the value and an error, if any.
-func Getenverror(key string) (value string, err error) {
-	if len(key) == 0 {
-		return "", ErrInvalid
-	}
-	val, found := syscall.Getenv(key)
-	if !found {
-		return "", ENOENV
-	}
-	return val, nil
-}
-
 // Getenv retrieves the value of the environment variable named by the key.
 // It returns the value, which will be empty if the variable is not present.
 func Getenv(key string) string {
-	v, _ := Getenverror(key)
+	v, _ := syscall.Getenv(key)
 	return v
 }
 

test/env.go

@@ -15,18 +15,14 @@ import (
 )
 
 func main() {
-	ga, e0 := os.Getenverror("GOARCH")
-	if e0 != nil {
-		print("$GOARCH: ", e0.Error(), "\n")
-		os.Exit(1)
-	}
+	ga := os.Getenv("GOARCH")
 	if ga != runtime.GOARCH {
 		print("$GOARCH=", ga, "!= runtime.GOARCH=", runtime.GOARCH, "\n")
 		os.Exit(1)
 	}
-	xxx, e1 := os.Getenverror("DOES_NOT_EXIST")
-	if e1 != os.ENOENV {
-		print("$DOES_NOT_EXIST=", xxx, "; err = ", e1.Error(), "\n")
+	xxx := os.Getenv("DOES_NOT_EXIST")
+	if xxx != "" {
+		print("$DOES_NOT_EXIST=", xxx, "\n")
 		os.Exit(1)
 	}
 }