terraform: match key lengths up in a diff

terraform/diff.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"sort"
+	"strings"
 	"sync"
 )
 
@@ -37,9 +38,13 @@ func (d *Diff) String() string {
 
 		buf.WriteString(name + "\n")
 
+		keyLen := 0
 		keys := make([]string, 0, len(rdiff.Attributes))
 		for key, _ := range rdiff.Attributes {
 			keys = append(keys, key)
+			if len(key) > keyLen {
+				keyLen = len(key)
+			}
 		}
 		sort.Strings(keys)
 
@@ -52,8 +57,9 @@ func (d *Diff) String() string {
 			}
 
 			buf.WriteString(fmt.Sprintf(
-				"  %s: %#v => %#v\n",
+				"  %s:%s %#v => %#v\n",
 				attrK,
+				strings.Repeat(" ", keyLen-len(attrK)),
 				attrDiff.Old,
 				v))
 		}

terraform/diff_test.go

@@ -18,6 +18,10 @@ func TestDiff_String(t *testing.T) {
 						Old:         "foo",
 						NewComputed: true,
 					},
+					"longfoo": &ResourceAttrDiff{
+						Old: "foo",
+						New: "bar",
+					},
 				},
 			},
 		},
@@ -32,6 +36,7 @@ func TestDiff_String(t *testing.T) {
 
 const diffStrBasic = `
 nodeA
-  bar: "foo" => "<computed>"
-  foo: "foo" => "bar"
+  bar:     "foo" => "<computed>"
+  foo:     "foo" => "bar"
+  longfoo: "foo" => "bar"
 `

terraform/terraform_test.go

@@ -401,6 +401,6 @@ const testTerraformDiffComputedStr = `
 aws_instance.bar
   foo: "" => "<computed>"
 aws_instance.foo
-  id: "" => "<computed>"
+  id:  "" => "<computed>"
   num: "" => "2"
 `