Add support for context.Context

command.go

@@ -17,6 +17,7 @@ package cobra
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -143,9 +144,11 @@ type Command struct {
 	// TraverseChildren parses flags on all parents before executing child command.
 	TraverseChildren bool
 
-	//FParseErrWhitelist flag parse errors to be ignored
+	// FParseErrWhitelist flag parse errors to be ignored
 	FParseErrWhitelist FParseErrWhitelist
 
+	ctx context.Context
+
 	// commands is the list of commands supported by this program.
 	commands []*Command
 	// parent is a parent command for this command.
@@ -205,6 +208,12 @@ type Command struct {
 	errWriter io.Writer
 }
 
+// Context returns underlying command context. If command wasn't
+// executed with ExecuteContext Context returns Background context.
+func (c *Command) Context() context.Context {
+	return c.ctx
+}
+
 // SetArgs sets arguments for the command. It is set to os.Args[1:] by default, if desired, can be overridden
 // particularly useful when testing.
 func (c *Command) SetArgs(a []string) {
@@ -860,6 +869,13 @@ 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.
+func (c *Command) ExecuteContext(ctx context.Context) error {
+	c.ctx = ctx
+	return c.Execute()
+}
+
 // Execute uses the args (os.Args[1:] by default)
 // and run through the command tree finding appropriate matches
 // for commands and then corresponding flags.
@@ -870,6 +886,10 @@ func (c *Command) Execute() error {
 
 // ExecuteC executes the command.
 func (c *Command) ExecuteC() (cmd *Command, err error) {
+	if c.ctx == nil {
+		c.ctx = context.Background()
+	}
+
 	// Regardless of what command execute is called on, run on Root only
 	if c.HasParent() {
 		return c.Root().ExecuteC()
@@ -914,6 +934,12 @@ func (c *Command) ExecuteC() (cmd *Command, err error) {
 		cmd.commandCalledAs.name = cmd.Name()
 	}
 
+	// We have to pass global context to children command
+	// if context is present on the parent command.
+	if cmd.ctx == nil {
+		cmd.ctx = c.ctx
+	}
+
 	err = cmd.execute(flags)
 	if err != nil {
 		// Always show help if requested, even if SilenceErrors is in
@@ -1558,7 +1584,7 @@ func (c *Command) ParseFlags(args []string) error {
 	beforeErrorBufLen := c.flagErrorBuf.Len()
 	c.mergePersistentFlags()
 
-	//do it here after merging all flags and just before parse
+	// do it here after merging all flags and just before parse
 	c.Flags().ParseErrorsWhitelist = flag.ParseErrorsWhitelist(c.FParseErrWhitelist)
 
 	err := c.Flags().Parse(args)

command_test.go

@@ -2,6 +2,7 @@ package cobra
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"os"
 	"reflect"
@@ -18,6 +19,16 @@ func executeCommand(root *Command, args ...string) (output string, err error) {
 	return output, err
 }
 
+func executeCommandWithContext(ctx context.Context, root *Command, args ...string) (output string, err error) {
+	buf := new(bytes.Buffer)
+	root.SetOutput(buf)
+	root.SetArgs(args)
+
+	err = root.ExecuteContext(ctx)
+
+	return buf.String(), err
+}
+
 func executeCommandC(root *Command, args ...string) (c *Command, output string, err error) {
 	buf := new(bytes.Buffer)
 	root.SetOutput(buf)
@@ -135,6 +146,62 @@ func TestSubcommandExecuteC(t *testing.T) {
 	}
 }
 
+func TestExecuteContext(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 := executeCommandWithContext(ctx, rootCmd, ""); err != nil {
+		t.Errorf("Root command must not fail: %+v", err)
+	}
+
+	if _, err := executeCommandWithContext(ctx, rootCmd, "child"); err != nil {
+		t.Errorf("Subcommand must not fail: %+v", err)
+	}
+
+	if _, err := executeCommandWithContext(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() {
+			t.Errorf("Command %s must have background context", cmd.Use)
+		}
+	}
+
+	rootCmd := &Command{Use: "root", Run: run, PreRun: run}
+	childCmd := &Command{Use: "child", Run: run, PreRun: run}
+	granchildCmd := &Command{Use: "grandchild", Run: run, PreRun: run}
+
+	childCmd.AddCommand(granchildCmd)
+	rootCmd.AddCommand(childCmd)
+
+	if _, err := executeCommand(rootCmd, ""); err != nil {
+		t.Errorf("Root command must not fail: %+v", err)
+	}
+
+	if _, err := executeCommand(rootCmd, "child"); err != nil {
+		t.Errorf("Subcommand must not fail: %+v", err)
+	}
+
+	if _, err := executeCommand(rootCmd, "child", "grandchild"); err != nil {
+		t.Errorf("Command child must not fail: %+v", err)
+	}
+}
+
 func TestRootUnknownCommandSilenced(t *testing.T) {
 	rootCmd := &Command{Use: "root", Run: emptyRun}
 	rootCmd.SilenceErrors = true