Pass context to completion (#1265)

command.go

@@ -887,7 +887,8 @@ func (c *Command) preRun() {
 }
 
 // ExecuteContext is the same as Execute(), but sets the ctx on the command.
-// Retrieve ctx by calling cmd.Context() inside your *Run lifecycle functions.
+// Retrieve ctx by calling cmd.Context() inside your *Run lifecycle or ValidArgs
+// functions.
 func (c *Command) ExecuteContext(ctx context.Context) error {
 	c.ctx = ctx
 	return c.Execute()
@@ -901,6 +902,14 @@ func (c *Command) Execute() error {
 	return err
 }
 
+// ExecuteContextC is the same as ExecuteC(), but sets the ctx on the command.
+// Retrieve ctx by calling cmd.Context() inside your *Run lifecycle or ValidArgs
+// functions.
+func (c *Command) ExecuteContextC(ctx context.Context) (*Command, error) {
+	c.ctx = ctx
+	return c.ExecuteC()
+}
+
 // ExecuteC executes the command.
 func (c *Command) ExecuteC() (cmd *Command, err error) {
 	if c.ctx == nil {

command_test.go

@@ -42,6 +42,17 @@ func executeCommandC(root *Command, args ...string) (c *Command, output string,
 	return c, buf.String(), err
 }
 
+func executeCommandWithContextC(ctx context.Context, root *Command, args ...string) (c *Command, output string, err error) {
+	buf := new(bytes.Buffer)
+	root.SetOut(buf)
+	root.SetErr(buf)
+	root.SetArgs(args)
+
+	c, err = root.ExecuteContextC(ctx)
+
+	return c, buf.String(), err
+}
+
 func resetCommandLineFlagSet() {
 	pflag.CommandLine = pflag.NewFlagSet(os.Args[0], pflag.ExitOnError)
 }
@@ -178,6 +189,35 @@ func TestExecuteContext(t *testing.T) {
 	}
 }
 
+func TestExecuteContextC(t *testing.T) {
+	ctx := context.TODO()
+
+	ctxRun := func(cmd *Command, args []string) {
+		if cmd.Context() != ctx {
+			t.Errorf("Command %q must have context when called with ExecuteContext", cmd.Use)
+		}
+	}
+
+	rootCmd := &Command{Use: "root", Run: ctxRun, PreRun: ctxRun}
+	childCmd := &Command{Use: "child", Run: ctxRun, PreRun: ctxRun}
+	granchildCmd := &Command{Use: "grandchild", Run: ctxRun, PreRun: ctxRun}
+
+	childCmd.AddCommand(granchildCmd)
+	rootCmd.AddCommand(childCmd)
+
+	if _, _, err := executeCommandWithContextC(ctx, rootCmd, ""); err != nil {
+		t.Errorf("Root command must not fail: %+v", err)
+	}
+
+	if _, _, err := executeCommandWithContextC(ctx, rootCmd, "child"); err != nil {
+		t.Errorf("Subcommand must not fail: %+v", err)
+	}
+
+	if _, _, err := executeCommandWithContextC(ctx, rootCmd, "child", "grandchild"); err != nil {
+		t.Errorf("Command child must not fail: %+v", err)
+	}
+}
+
 func TestExecute_NoContext(t *testing.T) {
 	run := func(cmd *Command, args []string) {
 		if cmd.Context() != context.Background() {

completions.go

@@ -221,6 +221,7 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 		// Unable to find the real command. E.g., <program> someInvalidCmd <TAB>
 		return c, []string{}, ShellCompDirectiveDefault, fmt.Errorf("Unable to find a command for arguments: %v", trimmedArgs)
 	}
+	finalCmd.ctx = c.ctx
 
 	// Check if we are doing flag value completion before parsing the flags.
 	// This is important because if we are completing a flag value, we need to also

completions_test.go

@@ -2,6 +2,7 @@ package cobra
 
 import (
 	"bytes"
+	"context"
 	"strings"
 	"testing"
 )
@@ -1203,6 +1204,48 @@ func TestFlagDirFilterCompletionInGo(t *testing.T) {
 	}
 }
 
+func TestValidArgsFuncCmdContext(t *testing.T) {
+	validArgsFunc := func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
+		ctx := cmd.Context()
+
+		if ctx == nil {
+			t.Error("Received nil context in completion func")
+		} else if ctx.Value("testKey") != "123" {
+			t.Error("Received invalid context")
+		}
+
+		return nil, ShellCompDirectiveDefault
+	}
+
+	rootCmd := &Command{
+		Use: "root",
+		Run: emptyRun,
+	}
+	childCmd := &Command{
+		Use:               "childCmd",
+		ValidArgsFunction: validArgsFunc,
+		Run:               emptyRun,
+	}
+	rootCmd.AddCommand(childCmd)
+
+	//nolint:golint,staticcheck // We can safely use a basic type as key in tests.
+	ctx := context.WithValue(context.Background(), "testKey", "123")
+
+	// Test completing an empty string on the childCmd
+	_, output, err := executeCommandWithContextC(ctx, rootCmd, ShellCompNoDescRequestCmd, "childCmd", "")
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	expected := strings.Join([]string{
+		":0",
+		"Completion ended with directive: ShellCompDirectiveDefault", ""}, "\n")
+
+	if output != expected {
+		t.Errorf("expected: %q, got: %q", expected, output)
+	}
+}
+
 func TestValidArgsFuncSingleCmd(t *testing.T) {
 	rootCmd := &Command{
 		Use:               "root",