Implement SetContext() for passing values between hooks #1118

edufschmidt · 2020-05-19T20:15:30Z

Implement SetContext() function for passing context between hooks, as proposed by @flimzy on issue How can I pass context.Context between pre/post-run hooks? #563. A test routine was too implemented, and validates that by using the newly introduced function together with persistent hooks, it is possible to pass values between hooks, and between parent and child commands.
Remove condition for passing down context to child command, as pointed out in issue Command context is not properly passed on to sub-commands #1109.

CLAassistant · 2020-05-19T20:15:35Z

All committers have signed the CLA.

Divya063 · 2020-06-17T09:47:10Z

@spf13 could you approve and merge this is PR?

aaronc · 2020-07-01T18:29:40Z

Would be great to see this get merged!

jackzampolin · 2020-07-14T18:42:19Z

Would really love to see this merged cc @eparis !

oriser · 2020-08-18T06:56:36Z

I will also be glad to see this merged :)

github-actions · 2020-10-18T00:25:26Z

This PR is being marked as stale due to a long period of inactivity

AWoelfel · 2020-10-27T10:16:31Z

I just stumbeled on this and would love to see this merged!

stapelberg · 2020-12-08T13:37:57Z

@jpmcb could you take a look at this simple PR please? I’m also interested in seeing this merged :)

Thanks!

jpmcb · 2021-01-22T22:52:10Z

command_test.go

@@ -148,6 +148,38 @@ func TestSubcommandExecuteC(t *testing.T) {
 	}
 }

+func TestSetContext(t *testing.T) {


Thanks for adding a test case for this!! 👍

jpmcb · 2021-01-22T22:53:16Z

command.go

-	if cmd.ctx == nil {
-		cmd.ctx = c.ctx
-	}
+	cmd.ctx = c.ctx


Why was the if removed here?

I can imagine, even with the addition of the new SetContext API, there still being the need for this if catch. The way I read this code now is that on every execution, a passed in command will always have it's context set.

This could even be a breaking change if during command execution, the users rely on the cmd.ctx not trickling down to subsequent child commands. This change makes the assumption that all sub-command executions should have the same context as the parent.

Please see #1109 for the motivation behind this change.

jpmcb · 2021-01-22T22:53:28Z

command.go

@@ -216,6 +216,12 @@ func (c *Command) Context() context.Context {
 	return c.ctx
 }

+// SetContext replaces the underlying command context so that parent
+// commands can pass down values to their subcommands.
+func (c *Command) SetContext(ctx context.Context) {


How is this any different from ExecuteContext? With using ExecuteContext, a user could pass in the necessary parent context, and then it is executed on the child sub-command.

If I'm not mistaken (it's been a while since this PR was submitted), by using ExecuteContext you're not able to set the context in the scope of a command so that nested commands have access to the new, modified context. In other words, the context is only passed to the root command, and then it is simply forwarded without modification to any subcommands. If you want parent commands to be able to act as middleware to their children, you need to have a structure that can be modified within the root context, which might not be desirable. That's where SetContext comes in handy. It allows to modify the context at will.

@jpmcb Any update? :) Thanks!

dfreilich · 2021-06-29T06:21:01Z

Any update on this PR? I was recently looking into this problem, and this would help my use case as well (ensuring that contexts are passed appropriately to deeply nested subcommands)

congon4tor · 2021-06-29T16:39:35Z

I believe this would also be useful for my use case. I want to initialise a grpc client that is common to all sub commands but some values to initialise it come from flags in the root command. The way I'm trying to achieve this is by having a PersistentPreRun on the root which initialises the grpc client and stores it in the context (with SetContext()). Then access the client from the sub commands with cmd.Context().

davidmdm · 2021-07-24T22:46:29Z

I too would really like this to get merged soon. it would allow for parent pre-runs to set values that child commands would need in a way that would really make my api less verbose.

alexykot · 2022-02-01T08:28:20Z

Hmm, seems like there were multiple attempts to fix this, but all PRs are either closed or still dangling. E.g. #1517, #1551.

I didn't look into details of competing solutions to have a preference here, but would be great to merge either of them to have this feature available.

johnSchnake · 2022-03-15T15:38:53Z

As part of #1600 I'm going through the backlog and found an issue related to supporting context. We now can get context but can't set the context. This PR seems to close the gap. I'm going to take a look at this and talk with the maintainers and see if we can (or why we can't) get this merged. See #563

stapelberg · 2022-03-15T15:48:18Z

Thanks very much! I’m still interested in having this functionality, so this is great news :)

marckhouzam · 2022-03-18T10:07:44Z

The ability to set a context has just been merged thanks to #1551. That PR, although opened more recently than this one, was limited to adding the SetContext() function, so we preferred that one.

If you are still interested in addressing #1109, which I don't fully grasp all the possible impacts with respect to backwards-compatibility, please open a new PR just for that issue and we will try to evaluate those impacts.

Thanks for you patience.

Basically the same as spf13/cobra#1517 but uses the `Set<field>` naming convention instead of `WithContext` Context setting without execution is important because it means that more design patterns can be achieved. Currently I am using functional options in a project and I can add behaviour through functional options as such: ```go type GrptlOption func(*cobra.Command) error func WithFileDescriptors(descriptors ...protoreflect.FileDescriptor) GrptlOption { return func(cmd *cobra.Command) error { err := CommandFromFileDescriptors(cmd, descriptors...) if err != nil { return err } return nil } } ``` I've got a lot more options and this pattern allows me to have nice abstracted pieces of logic that interact with the cobra command. This Pattern also allows for adding extra information to a call through `PreRun` functions: ```go cmd := &cobra.Command{ Use: "Foobar", PersistentPreRun: func(cmd *cobra.Command, args []string) { err :=cmd.SetContext(metadata.AppendToOutgoingContext(context.Background(), "pre", "run")) }, } ``` This is a veer nice abstraction and allows for these functions to be very modular The issue I'm facing at the moment is that I can't write a nifty option (something like `WithAuthentication`) because that needs access to reading and setting the context. Currently I can only read the context. Needing to use `ExecuteContext` breaks this abstraction because I need to run it right at the end. Merge spf13/cobra#1551 Fixes spf13/cobra#1517 Fixes spf13/cobra#1118 Fixes spf13/cobra#563

edufschmidt added 3 commits May 19, 2020 17:07

Add SetContext() function to cobra.Command

d58c46a

Remove condition for passing ctx to child command

a081152

Create TestSetContext() for testing passing context between hooks

d0e2899

alexanderbez mentioned this pull request Jul 1, 2020

CLI Refactor cosmos/cosmos-sdk#6571

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exdx mentioned this pull request Apr 14, 2021

Create and set timeouts globally via a flag operator-framework/kubectl-operator#43

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Is there a way to share variables inside cobra instance? #1289

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Implement SetContext() for passing values between hooks #1118

Implement SetContext() for passing values between hooks #1118

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alexykot commented Feb 1, 2022

johnSchnake commented Mar 15, 2022

stapelberg commented Mar 15, 2022

marckhouzam commented Mar 18, 2022

Implement SetContext() for passing values between hooks #1118

Implement SetContext() for passing values between hooks #1118

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