provider/aws: Improve validation of configs

builtin/providers/aws/resource_provider.go

@@ -2,6 +2,7 @@ package aws
 
 import (
 	"log"
+	"os"
 
 	"github.com/hashicorp/terraform/helper/config"
 	"github.com/hashicorp/terraform/helper/multierror"
@@ -26,14 +27,30 @@ type ResourceProvider struct {
 }
 
 func (p *ResourceProvider) Validate(c *terraform.ResourceConfig) ([]string, []error) {
-	v := &config.Validator{
-		Optional: []string{
-			"access_key",
-			"secret_key",
-			"region",
-		},
+	type param struct {
+		env string
+		key string
+	}
+	params := []param{
+		{"AWS_REGION", "region"},
+		{"AWS_ACCESS_KEY", "access_key"},
+		{"AWS_SECRET_KEY", "secret_key"},
 	}
 
+	var optional []string
+	var required []string
+	for _, p := range params {
+		if v := os.Getenv(p.env); v != "" {
+			optional = append(optional, p.key)
+		} else {
+			required = append(required, p.key)
+		}
+	}
+
+	v := &config.Validator{
+		Required: required,
+		Optional: optional,
+	}
 	return v.Validate(c)
 }