x/build: make a bot review CLs for common mistakes (like Tricorder)

[bradfitz]

Tracking bug to write a bot to review CLs for common mistakes:

• properly-formatted references to CLs and bugs
• conventional subject ("pkg/name: lowercase verb, not period at end")
• gofmt
• missing copyright headers

And whatever else we add in the future.

(forked from email thread https://groups.google.com/forum/#!topic/golang-dev/KpHMoePhg6c)

/cc @kevinburke @rsc

[dsnet]

What about lint and vet?

[bradfitz]

What about lint and vet?

Sure. I imagine we'd start with some basic things and once we have it automated, we can add more to it later. I wouldn't make lint & vet a requirement for the initial deployment.

[kevinburke]

IIRC @josharian has been working on getting golang/go to pass vet, but it doesn't currently, and relies on an "exemption" file for places/test files that don't pass vet on purpose.

[mvdan]

gofmt

Perhaps with -s?

properly-formatted references to CLs and bugs

Github has various accepted formats for these (https://help.github.com/articles/closing-issues-via-commit-messages/). I assume you want to limit it to "Fixes #n", though?

[bradfitz]

@mvdan, the two common mistakes I'm thinking of:

1. people write "Fixes #nnn" when they're hacking in a subrepo, and thus Github requires the fully-qualifed "Fixes golang/go#nnn" format, since Go only uses one massive bug tracker, instead of per-repo bug trackers.
2. people sometimes accidentally refer to CL numbers with the # sign, spamming ancient bugs. They should write "CL nnnn" or golang.org/cl/nnnn instead of "CL #nnn" or "change #nnn".

[ianlancetaylor]

Another common mistake is using a git SHA when they should use a CL number.

[mvdan]

Another thing that comes to mind is gerrit/github links that should be golang.org/issue/X or golang.org/cl/Y.

[minux]

I'd also like the bot to catch accidentally committing a binary, which happened at least five times (the following list is not comprehensive as I just looked at the top 12 largest files): https://golang.org/cl/4287056 1179384 bytes https://golang.org/cl/4406044 3500057 bytes https://golang.org/cl/9560 6084208 bytes https://golang.org/cl/19968 2243120 bytes I also remember one time we rewrote the git history to remove one accidentally committed binary file. I once suggested that we change Gerrit setting to reject binary files bigger than a certain size, but that was rejected. If we make such a pre-check bot, we can at least make it point out a binary file is included (and its size). This will be a warning. Another idea about spamming old bugs, also checks for tiny issue numbers (say, less than 100), because people sometimes use #1 as bulletpoints and some test output use #X as a short "Number X", I remember runtime/pprof tests do this.

[minux]

On Fri, Jan 6, 2017 at 4:31 PM, Ian Lance Taylor ***@***.***> wrote: Another common mistake is using a git SHA when they should use a CL number.

I'd like the bot to be more helpful and actually figure out the correct CL number for the git commit hash and suggest its use.

[bradfitz]

I also remember one time we rewrote the git history to
remove one accidentally committed binary file.

I have no memory of this and am pretty sure we have never rewritten the Git history.

[ianlancetaylor]

We rewrote people's memory along with the git history, to simplify matters going forward.

[minux]

On Fri, Jan 6, 2017 at 4:57 PM, Brad Fitzpatrick ***@***.***> wrote: I also remember one time we rewrote the git history to remove one accidentally committed binary file. I have no memory of this and am pretty sure we have never rewritten the Git history.

Sorry, my memory is indeed off. It's not to remove a binary file, but to revert a bad merge. https://groups.google.com/d/msg/golang-dev/2wkzNtLKWyI/bl3wVhNAIm4J It is to remove these two commits: https://golang.org/cl/5351/, commit https://go.googlesource.com/go/+/c21f1d5ef30ff52cb42fca146a9c7161dfee5c3c https://golang.org/cl/5353/, commit https://go.googlesource.com/go/+/e5048a5eaabdb86156d8de1a97d32eb898560e50

[LionNatsu]

Maybe we can add some pre-check in git-codereview? After change and before mail

[kevinburke]

@LionNatsu from the email thread:

We could have a bot that leaves comments on Gerrit for common mistakes. I'd prefer that over CLI tooling. (Not everybody uses git-codereview, especially if we start accepting Github PRs)

[LionNatsu]

@kevinburke Oh, indeed.

[shawnps]

I'm interested in working on this (I wrote Go Report Card https://goreportcard.com/ with @hermanschaaf which does a lot of this too).

Edit: the Go Report Card reference was just to mention that I've worked on a similar problem before and could maybe borrow some code from there.

[bradfitz]

@shawnps, the first thing to figure out is where this runs and how, and how it interacts with Gerrit.

We already have one process polling Gerrit (the build coordinator's "watcher"), and if we revamp dev.golang.org that would be a second. This would be a third. I suspect we'll want to make this bot interact with the proposed dev.golang.org all-Github-and-Gerrit-in-RAM server, and then this bot could long-poll our new "Github/Gerrit Model Server" waiting for changes (new or updated CLs).

But in the meantime I suppose it could run manually every N minutes. Please use https://godoc.org/golang.org/x/build/gerrit which we already use. If something's missing, modify that package as needed.

You'll want to store state somewhere. It's easy to find CLs the bot's already left comments on, but the bot should probably be silent and not +1 the bug if there's nothing to say, which means you'll need to store state about which bugs you've seen and are happy about. That should probably go into Google Cloud Datastore (https://cloud.google.com/datastore/) which we already use in the Go build system (see "git grep datastore" in src/golang.org/x/build/cmd/coordinator), as opposed to files on the local filesystem. (Filesystems come and go as we destroy and recreate the world)

[shawnps]

@bradfitz thanks, I was just about to ask about many of the details you just listed. Taking a look at https://godoc.org/golang.org/x/build/gerrit now.

That should probably go into Google Cloud Datastore (https://cloud.google.com/datastore/) which we already use in the Go build system (see "git grep datastore" in src/golang.org/x/build/cmd/coordinator)

Found datastore reference here:

https://github.com/golang/build/blob/master/cmd/coordinator/gce.go#L119

So this particular app (coordinator) "runs on CoreOS on Google Compute Engine and manages builds using Docker containers and/or VMs as needed" - is the suggestion that the new bot would run on GCE or GAE in a similar manner to this one?

[bradfitz]

Yes, this would run on GCE somewhere.

I would start by making it a non-package main package that you can instantiate and run. Then make a tiny tiny package main runner program for it for development and local testing.

Once it's working, we can integrate that bot into something.

I also imagine that some helper environment will need to be described by a Dockerfile, since you'll want things like golint and go vet available.

[shawnps]

Okay thanks. As a first step I'm currently trying to figure out how to grab files for a specific change on Gerrit in order to run gofmt on them.

[bradfitz]

Okay thanks. As a first step I'm currently trying to figure out how to grab files for a specific change on Gerrit in order to run gofmt on them.

Click "Download" in the web UI for a hint:

git fetch https://go.googlesource.com/crypto refs/changes/79/34779/8 && git cherry-pick FETCH_HEAD

You can have the bot do a shallow git clone of the parent git commit, and then chrery-pick atop that.

Alternatively, there's an API to get files from Gerrit at a specific revision as a tarball. See the cmd/coordinator code:

func getSourceTgzFromGerrit(repo, rev string) (tgz []byte, err error) {
        return getSourceTgzFromURL("gerrit", repo, rev, "https://go.googlesource.com/"+repo+"/+archive/"+rev+".tar.gz")
}

[shawnps]

@bradfitz thanks, I had gotten as far as getting the FetchInfo:

package main

import (
	"fmt"
	"log"

	"golang.org/x/build/gerrit"
)

func main() {
	c := gerrit.NewClient("https://go-review.googlesource.com", gerrit.NoAuth)
	cis, err := c.QueryChanges("34871", gerrit.QueryChangesOpt{
		N: 5000,
		Fields: []string{
			"CURRENT_FILES",
			"CURRENT_REVISION",
		},
	})
	if err != nil {
		log.Fatal(err)
	}
	for _, r := range cis[0].Revisions {
		for _, f := range r.Fetch {
			fmt.Println(f)
		}
	}
}

(I know the cis[0] could panic if nothing is returned, this was just a quick test to see how far I could get right now)

I guess I can use this to get this piece: refs/changes/79/34779/8 and then do the cloning bit as you mentioned.

[shawnps]

@bradfitz let me know if that looks like I'm on the right track, will be offline soon but I'll pick this back up in the morning. I appreciate all the feedback and help, thanks!

[bradfitz]

Rather than do a query for "34871", you probably just want to load the detail of a single change using https://godoc.org/golang.org/x/build/gerrit#Client.GetChangeDetail

[shawnps]

@bradfitz any idea if there's a reason why GetChangeDetail doesn't take an optional gerrit.QueryChangesOpt? I was planning to go the tar.gz route but that requires the revision, which doesn't seem to be accessible unless you specify "CURRENT_REVISION".

[bradfitz]

IIRC, GetChangeDetail returns everything already, so there's no need to selectively say what you want?

If not, we can modify that package as needed.

[shawnps]

@bradfitz I will dig a bit more but I think I need the current revision in order to get the tarball, and current revision only appears in ChangeInfo if you request it:

https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#change-info

see "current_revision":

"Only set if the current revision is requested or if all revisions are requested."

But maybe this is my misunderstanding of how revisions work in Gerrit.

[shawnps]

@bradfitz I was able to get the revision info with this patch:

diff --git a/gerrit/gerrit.go b/gerrit/gerrit.go
index fbdc7a8..b983d90 100644
--- a/gerrit/gerrit.go
+++ b/gerrit/gerrit.go
@@ -345,9 +345,19 @@ func (c *Client) QueryChanges(q string, opts ...QueryChangesOpt) ([]*ChangeInfo,
 // GetChangeDetail retrieves a change with labels, detailed labels, detailed
 // accounts, and messages.
 // For the API call, see https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#get-change-detail
-func (c *Client) GetChangeDetail(changeID string) (*ChangeInfo, error) {
+func (c *Client) GetChangeDetail(changeID string, opts ...QueryChangesOpt) (*ChangeInfo, error) {
+	var opt QueryChangesOpt
+	switch len(opts) {
+	case 0:
+	case 1:
+		opt = opts[0]
+	default:
+		return nil, errors.New("only 1 option struct supported")
+	}
 	var change ChangeInfo
-	err := c.do(&change, "GET", "/changes/"+changeID+"/detail")
+	err := c.do(&change, "GET", "/changes/"+changeID+"/detail", urlValues{
+		"o": opt.Fields,
+	})
 	if err != nil {
 		return nil, err
 	}

without this, I've found ci.Revisions to be empty

[shawnps]

CL made here for the above diff: https://go-review.googlesource.com/#/c/34922/

[bradfitz]

We had a long-running dup bug that I just closed, but contains discussion and links: #20648