From e556bb89345ebf08980514f1b516c5911ab21d4e Mon Sep 17 00:00:00 2001
From: Jarek Potiuk <jarek.potiuk@polidea.com>
Date: Sat, 4 Jan 2020 14:47:55 +0100
Subject: [PATCH] Adds pagination to Github request.

Fixes #3.

Unfortunately most of the Github APIs returning collections returns maximum 30
responses. This is documented here https://developer.github.com/v3/#pagination
but unfortunately it is not mentioned in the particular APIs that are affected.
So when reading https://developer.github.com/v3/pulls/#list-pull-requests it's
not at all obvious that pagination is in operation and that you should add
another loop through pages.

Periodic labeler does not have pagination implemented, therefore the result is
that in big repositories with > 30 PRs only the OLDEST prs will be checked
(that's what is the sorting order). If all those 30 PRs are properly labelled,
then the plugin will stop working and will not pick any new PRs. There is an
interesting behaviour of that - if there are unlabelled old PRs, they will get
updated, so - in fact - they will disappear from the "oldest" list and possibly
some new PRs that will be checked in the new pass. However once you have 30
oldest, properly labelled PRs, the plugin stops working. That's really annoying
and difficult to detect problem - especially if your repo does not have a lot
of PRs.

Pagination is easy. It is described here:
https://github.com/google/go-github/#pagination
---
 main.go | 43 +++++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/main.go b/main.go
index d3a900c..8b3080f 100644
--- a/main.go
+++ b/main.go
@@ -2,9 +2,9 @@ package main
 
 import (
 	"context"
-	"strings"
 	"os"
 	"path"
+	"strings"
 
 	"github.com/golang/glog"
 	"golang.org/x/oauth2"
@@ -14,13 +14,13 @@ import (
 )
 
 func contains(slice []string, item string) bool {
-    set := make(map[string]struct{}, len(slice))
-    for _, s := range slice {
-        set[s] = struct{}{}
-    }
+	set := make(map[string]struct{}, len(slice))
+	for _, s := range slice {
+		set[s] = struct{}{}
+	}
 
-    _, ok := set[item]
-    return ok
+	_, ok := set[item]
+	return ok
 }
 
 func getCurrentLabels(pr *github.PullRequest) []string {
@@ -33,7 +33,7 @@ func getCurrentLabels(pr *github.PullRequest) []string {
 
 func containsLabels(expected []string, current []string) bool {
 	for _, e := range expected {
-		if ! contains(current, e) {
+		if !contains(current, e) {
 			return false
 		}
 	}
@@ -97,18 +97,25 @@ func main() {
 	}
 
 	opt := &github.PullRequestListOptions{State: "open", Sort: "updated"}
-	pulls, _, err := client.PullRequests.List(context.Background(), owner, repo, opt)
-	if err != nil {
-		glog.Fatal(err)
-	}
-	for _, pull := range pulls {
-		files, _, err := client.PullRequests.ListFiles(context.Background(), owner, repo, *pull.Number, nil)
+	// get all pages of results
+	for {
+		pulls, resp, err := client.PullRequests.List(context.Background(), owner, repo, opt)
 		if err != nil {
-			glog.Error(err)
+			glog.Fatal(err)
+		}
+		for _, pull := range pulls {
+			files, _, err := client.PullRequests.ListFiles(context.Background(), owner, repo, *pull.Number, nil)
+			if err != nil {
+				glog.Error(err)
+			}
+			expectedLabels := matchFiles(labelMatchers, files)
+			if !containsLabels(expectedLabels, getCurrentLabels(pull)) {
+				client.Issues.AddLabelsToIssue(context.Background(), owner, repo, *pull.Number, expectedLabels)
+			}
 		}
-		expectedLabels := matchFiles(labelMatchers, files)
-		if ! containsLabels(expectedLabels, getCurrentLabels(pull)) {
-			client.Issues.AddLabelsToIssue(context.Background(), owner, repo, *pull.Number, expectedLabels)
+		if resp.NextPage == 0 {
+			break
 		}
+		opt.Page = resp.NextPage
 	}
 }