gopls/internal/telemetry/cmd/stacks: paginate issue search

The GitHub API returns at most 100 results per page, but gopls already
has 101 issues, so we are dropping issues and need pagination.

The GitHub search API has a hard limit of 1000 results
(https://docs.github.com/en/rest/search/search?apiVersion=2022-11-28#about-search),
which we'll hit eventually.

As an alternative, use the "List repository issues" API
(https://docs.github.com/en/rest/issues/issues?apiVersion=2022-11-28#list-repository-issues).
This allows filtering by label, which is all we need.

Note that the old code was mistakenly searching all of GitHub, not just
golang/go. That is now fixed.

GitHub pagination uses an awkward header format
(https://docs.github.com/en/rest/using-the-rest-api/using-pagination-in-the-rest-api?apiVersion=2022-11-28),
but it is ultimately just ?page=1, ?page=2, etc, so we just keep trying
new pages until we get no more results.

Updates golang/go#71045.

Change-Id: I6a6a636ccc17c9e1b1024369f98965f59456896a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/642436
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: prattmic

gopls/internal/telemetry/cmd/stacks/stacks.go

@@ -391,19 +391,14 @@ func readReports(pcfg ProgramConfig, days int) (stacks map[string]map[Info]int64
 // predicates.
 func readIssues(pcfg ProgramConfig) ([]*Issue, error) {
 	// Query GitHub for all existing GitHub issues with the report label.
-	//
-	// TODO(adonovan): by default GitHub returns at most 30
-	// issues; we have lifted this to 100 using per_page=%d, but
-	// that won't work forever; use paging.
-	query := fmt.Sprintf("is:issue label:%s", pcfg.SearchLabel)
-	res, err := searchIssues(query)
+	issues, err := searchIssues(pcfg.SearchLabel)
 	if err != nil {
-		log.Fatalf("GitHub issues query %q failed: %v", query, err)
+		log.Fatalf("GitHub issues label %q search failed: %v", pcfg.SearchLabel, err)
 	}
 
 	// Extract and validate predicate expressions in ```#!stacks...``` code blocks.
 	// See the package doc comment for the grammar.
-	for _, issue := range res.Items {
+	for _, issue := range issues {
 		block := findPredicateBlock(issue.Body)
 		if block != "" {
 			expr, err := parser.ParseExpr(block)
@@ -480,7 +475,7 @@ func readIssues(pcfg ProgramConfig) ([]*Issue, error) {
 		}
 	}
 
-	return res.Items, nil
+	return issues, nil
 }
 
 // claimStack maps each stack ID to its issue (if any).
@@ -798,28 +793,58 @@ func frameURL(pclntab map[string]FileLine, info Info, frame string) string {
 // -- GitHub search --
 
 // searchIssues queries the GitHub issue tracker.
-func searchIssues(query string) (*IssuesSearchResult, error) {
-	q := url.QueryEscape(query)
+func searchIssues(label string) ([]*Issue, error) {
+	label = url.QueryEscape(label)
 
-	req, err := http.NewRequest("GET", "https://api.github.com/search/issues?q="+q+"&per_page=100", nil)
-	if err != nil {
-		return nil, err
-	}
-	req.Header.Add("Authorization", "Bearer "+authToken)
-	resp, err := http.DefaultClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer resp.Body.Close()
-	if resp.StatusCode != http.StatusOK {
-		body, _ := io.ReadAll(resp.Body)
-		return nil, fmt.Errorf("search query failed: %s (body: %s)", resp.Status, body)
+	// Slurp all issues with the telemetry label.
+	//
+	// The pagination link headers have an annoying format, but ultimately
+	// are just ?page=1, ?page=2, etc with no extra state. So just keep
+	// trying new pages until we get no more results.
+	//
+	// NOTE: With this scheme, GitHub clearly has no protection against
+	// race conditions, so presumably we could get duplicate issues or miss
+	// issues across pages.
+
+	getPage := func(page int) ([]*Issue, error) {
+		url := fmt.Sprintf("https://api.github.com/repos/golang/go/issues?state=all&labels=%s&per_page=100&page=%d", label, page)
+		req, err := http.NewRequest("GET", url, nil)
+		if err != nil {
+			return nil, err
+		}
+		req.Header.Add("Authorization", "Bearer "+authToken)
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			return nil, err
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			body, _ := io.ReadAll(resp.Body)
+			return nil, fmt.Errorf("search query %s failed: %s (body: %s)", url, resp.Status, body)
+		}
+		var r []*Issue
+		if err := json.NewDecoder(resp.Body).Decode(&r); err != nil {
+			return nil, err
+		}
+
+		return r, nil
 	}
-	var result IssuesSearchResult
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-		return nil, err
+
+	var results []*Issue
+	for page := 1; ; page++ {
+		r, err := getPage(page)
+		if err != nil {
+			return nil, err
+		}
+		if len(r) == 0 {
+			// No more results.
+			break
+		}
+
+		results = append(results, r...)
 	}
-	return &result, nil
+
+	return results, nil
 }
 
 // updateIssueBody updates the body of the numbered issue.
@@ -882,12 +907,7 @@ func addIssueComment(number int, comment string) error {
 	return nil
 }
 
-// See https://developer.github.com/v3/search/#search-issues.
-
-type IssuesSearchResult struct {
-	TotalCount int `json:"total_count"`
-	Items      []*Issue
-}
+// See https://docs.github.com/en/rest/issues/issues?apiVersion=2022-11-28#list-repository-issues.
 
 type Issue struct {
 	Number    int