From 15fecb0bf348d4c5c7deb8094de5e8b3900d0412 Mon Sep 17 00:00:00 2001
From: Justin Cormack <justin.cormack@docker.com>
Date: Mon, 8 Aug 2016 15:08:55 +0100
Subject: [PATCH] More helpful error message when not sufficiently
 argumentative

The error message suggests you need one argument even when you
have provided one. Suggest having another argument.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Upstream-commit: 4ce93940b7c2a640c94296f20352cf6f052d1028
Component: engine
---
 .../engine/builder/dockerfile/dispatchers.go  |  8 +++++--
 .../builder/dockerfile/dispatchers_test.go    | 22 +++++++++++++++++--
 .../builder/dockerfile/evaluator_test.go      |  2 +-
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/components/engine/builder/dockerfile/dispatchers.go b/components/engine/builder/dockerfile/dispatchers.go
index dd237c10be..dc5b7ef0b8 100644
--- a/components/engine/builder/dockerfile/dispatchers.go
+++ b/components/engine/builder/dockerfile/dispatchers.go
@@ -155,7 +155,7 @@ func label(b *Builder, args []string, attributes map[string]bool, original strin
 //
 func add(b *Builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) < 2 {
-		return errAtLeastOneArgument("ADD")
+		return errAtLeastTwoArguments("ADD")
 	}
 
 	if err := b.flags.Parse(); err != nil {
@@ -171,7 +171,7 @@ func add(b *Builder, args []string, attributes map[string]bool, original string)
 //
 func dispatchCopy(b *Builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) < 2 {
-		return errAtLeastOneArgument("COPY")
+		return errAtLeastTwoArguments("COPY")
 	}
 
 	if err := b.flags.Parse(); err != nil {
@@ -760,6 +760,10 @@ func errExactlyOneArgument(command string) error {
 	return fmt.Errorf("%s requires exactly one argument", command)
 }
 
+func errAtLeastTwoArguments(command string) error {
+	return fmt.Errorf("%s requires at least two arguments", command)
+}
+
 func errTooManyArguments(command string) error {
 	return fmt.Errorf("Bad input to %s, too many arguments", command)
 }
diff --git a/components/engine/builder/dockerfile/dispatchers_test.go b/components/engine/builder/dockerfile/dispatchers_test.go
index 75d1185a0f..22ff66a68c 100644
--- a/components/engine/builder/dockerfile/dispatchers_test.go
+++ b/components/engine/builder/dockerfile/dispatchers_test.go
@@ -43,8 +43,6 @@ func TestCommandsAtLeastOneArgument(t *testing.T) {
 	commands := []commandWithFunction{
 		{"ENV", func(args []string) error { return env(nil, args, nil, "") }},
 		{"LABEL", func(args []string) error { return label(nil, args, nil, "") }},
-		{"ADD", func(args []string) error { return add(nil, args, nil, "") }},
-		{"COPY", func(args []string) error { return dispatchCopy(nil, args, nil, "") }},
 		{"ONBUILD", func(args []string) error { return onbuild(nil, args, nil, "") }},
 		{"EXPOSE", func(args []string) error { return expose(nil, args, nil, "") }},
 		{"VOLUME", func(args []string) error { return volume(nil, args, nil, "") }}}
@@ -64,6 +62,26 @@ func TestCommandsAtLeastOneArgument(t *testing.T) {
 	}
 }
 
+func TestCommandsAtLeastTwoArguments(t *testing.T) {
+	commands := []commandWithFunction{
+		{"ADD", func(args []string) error { return add(nil, args, nil, "") }},
+		{"COPY", func(args []string) error { return dispatchCopy(nil, args, nil, "") }}}
+
+	for _, command := range commands {
+		err := command.function([]string{"arg1"})
+
+		if err == nil {
+			t.Fatalf("Error should be present for %s command", command.name)
+		}
+
+		expectedError := fmt.Sprintf("%s requires at least two arguments", command.name)
+
+		if err.Error() != expectedError {
+			t.Fatalf("Wrong error message for %s. Got: %s. Should be: %s", command.name, err.Error(), expectedError)
+		}
+	}
+}
+
 func TestCommandsTooManyArguments(t *testing.T) {
 	commands := []commandWithFunction{
 		{"ENV", func(args []string) error { return env(nil, args, nil, "") }},
diff --git a/components/engine/builder/dockerfile/evaluator_test.go b/components/engine/builder/dockerfile/evaluator_test.go
index 75248f0d10..6a004170e1 100644
--- a/components/engine/builder/dockerfile/evaluator_test.go
+++ b/components/engine/builder/dockerfile/evaluator_test.go
@@ -28,7 +28,7 @@ func initDispatchTestCases() []dispatchTestCase {
 		dockerfile: `COPY
 	quux \
       bar`,
-		expectedError: "COPY requires at least one argument",
+		expectedError: "COPY requires at least two arguments",
 	},
 		{
 			name:          "ONBUILD forbidden FROM",