Add e2e tests for plugin vs global argument issues

These won't pass right now due to https://github.com/docker/cli/issues/1699
("Plugins can't re-use the same flags as cli global flags") and the change in
935d47bbe9 ("Ignore unknown arguments on the top-level command."), but the
intention is to fix them now.

Signed-off-by: Ian Campbell <ijc@docker.com>

e2e/cli-plugins/flags_test.go

@@ -3,6 +3,8 @@ package cliplugins
 import (
 	"testing"
 
+	"gotest.tools/assert"
+	is "gotest.tools/assert/cmp"
 	"gotest.tools/icmd"
 )
 
@@ -17,3 +19,82 @@ func TestRunGoodArgument(t *testing.T) {
 		Out:      "Hello Cleveland!",
 	})
 }
+
+// TestClashWithGlobalArgs ensures correct behaviour when a plugin
+// has an argument with the same name as one of the globals.
+func TestClashWithGlobalArgs(t *testing.T) {
+	run, _, cleanup := prepare(t)
+	defer cleanup()
+
+	for _, tc := range []struct {
+		name                     string
+		args                     []string
+		expectedOut, expectedErr string
+	}{
+		{
+			name:        "short-without-val",
+			args:        []string{"-D"},
+			expectedOut: "Hello World!",
+			expectedErr: "Plugin debug mode enabled",
+		},
+		{
+			name:        "long-without-val",
+			args:        []string{"--debug"},
+			expectedOut: "Hello World!",
+			expectedErr: "Plugin debug mode enabled",
+		},
+		{
+			name:        "short-with-val",
+			args:        []string{"-c", "Christmas"},
+			expectedOut: "Merry Christmas!",
+			expectedErr: "",
+		},
+		{
+			name:        "short-with-val",
+			args:        []string{"--context", "Christmas"},
+			expectedOut: "Merry Christmas!",
+			expectedErr: "",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			args := append([]string{"helloworld"}, tc.args...)
+			res := icmd.RunCmd(run(args...))
+			res.Assert(t, icmd.Expected{
+				ExitCode: 0,
+				Out:      tc.expectedOut,
+				Err:      tc.expectedErr,
+			})
+		})
+	}
+}
+
+// TestUnknownGlobal checks that unknown globals report errors
+func TestUnknownGlobal(t *testing.T) {
+	run, _, cleanup := prepare(t)
+	defer cleanup()
+
+	t.Run("no-val", func(t *testing.T) {
+		res := icmd.RunCmd(run("--unknown", "helloworld"))
+		res.Assert(t, icmd.Expected{
+			ExitCode: 125,
+		})
+		assert.Assert(t, is.Equal(res.Stdout(), ""))
+		assert.Assert(t, is.Contains(res.Stderr(), "unknown flag: --unknown"))
+	})
+	t.Run("separate-val", func(t *testing.T) {
+		res := icmd.RunCmd(run("--unknown", "foo", "helloworld"))
+		res.Assert(t, icmd.Expected{
+			ExitCode: 125,
+		})
+		assert.Assert(t, is.Equal(res.Stdout(), ""))
+		assert.Assert(t, is.Contains(res.Stderr(), "unknown flag: --unknown"))
+	})
+	t.Run("joined-val", func(t *testing.T) {
+		res := icmd.RunCmd(run("--unknown=foo", "helloworld"))
+		res.Assert(t, icmd.Expected{
+			ExitCode: 125,
+		})
+		assert.Assert(t, is.Equal(res.Stdout(), ""))
+		assert.Assert(t, is.Contains(res.Stderr(), "unknown flag: --unknown"))
+	})
+}

e2e/cli-plugins/testdata/docker-help-helloworld.golden

@@ -4,7 +4,9 @@ Usage:	docker helloworld [OPTIONS] COMMAND
 A basic Hello World plugin for tests
 
 Options:
-      --who string   Who are we addressing?
+  -c, --context string   Is it Christmas?
+  -D, --debug            Enable debug
+      --who string       Who are we addressing?
 
 Commands:
   apiversion  Print the API version of the server