Deal with 202 Accepted Status Code

Fixes #486.
Closes #488.

Change-Id: I31ff003552dbffaca78c740b89d54150b81c525c

README.md

@@ -99,6 +99,23 @@ if _, ok := err.(*github.RateLimitError); ok {
 Learn more about GitHub rate limiting at
 http://developer.github.com/v3/#rate-limiting.
 
+### Accepted Status ###
+
+Some endpoints may return a 202 Accepted status code, meaning that the
+information required is not yet ready and was scheduled to be gathered on
+the GitHub side. Methods known to behave like this are documented specifying
+this behavior.
+
+To detect this condition of error, you can check if its type is
+`*github.AcceptedError`:
+
+```go
+stats, _, err := client.Repositories.ListContributorsStats(org, repo)
+if _, ok := err.(*github.AcceptedError); ok {
+	log.Println("scheduled on GitHub side")
+}
+```
+
 ### Conditional Requests ###
 
 The GitHub API has good support for conditional requests which will help

github/doc.go

@@ -86,6 +86,21 @@ To detect an API rate limit error, you can check if its type is *github.RateLimi
 Learn more about GitHub rate limiting at
 http://developer.github.com/v3/#rate-limiting.
 
+Accepted Status
+
+Some endpoints may return a 202 Accepted status code, meaning that the
+information required is not yet ready and was scheduled to be gathered on
+the GitHub side. Methods known to behave like this are documented specifying
+this behavior.
+
+To detect this condition of error, you can check if its type is
+*github.AcceptedError:
+
+	stats, _, err := client.Repositories.ListContributorsStats(org, repo)
+	if _, ok := err.(*github.AcceptedError); ok {
+		log.Println("scheduled on GitHub side")
+	}
+
 Conditional Requests
 
 The GitHub API has good support for conditional requests which will help

github/github.go

@@ -501,6 +501,18 @@ func (r *RateLimitError) Error() string {
 		r.Response.StatusCode, r.Message, r.Rate.Reset.Time.Sub(time.Now()))
 }
 
+// AcceptedError occurs when GitHub returns 202 Accepted response with an
+// empty body, which means a job was scheduled on the GitHub side to process
+// the information needed and cache it.
+// Technically, 202 Accepted is not a real error, it's just used to
+// indicate that results are not ready yet, but should be available soon.
+// The request can be repeated after some time.
+type AcceptedError struct{}
+
+func (*AcceptedError) Error() string {
+	return "job scheduled on GitHub side; try again later"
+}
+
 // AbuseRateLimitError occurs when GitHub returns 403 Forbidden response with the
 // "documentation_url" field value equal to "https://developer.github.com/v3#abuse-rate-limits".
 type AbuseRateLimitError struct {
@@ -564,14 +576,19 @@ func (e *Error) Error() string {
 }
 
 // CheckResponse checks the API response for errors, and returns them if
-// present.  A response is considered an error if it has a status code outside
-// the 200 range.  API error responses are expected to have either no response
+// present. A response is considered an error if it has a status code outside
+// the 200 range or equal to 202 Accepted.
+// API error responses are expected to have either no response
 // body, or a JSON response body that maps to ErrorResponse.  Any other
 // response body will be silently ignored.
 //
 // The error type will be *RateLimitError for rate limit exceeded errors,
+// *AcceptedError for 202 Accepted status codes,
 // and *TwoFactorAuthError for two-factor authentication errors.
 func CheckResponse(r *http.Response) error {
+	if r.StatusCode == http.StatusAccepted {
+		return &AcceptedError{}
+	}
 	if c := r.StatusCode; 200 <= c && c <= 299 {
 		return nil
 	}

github/repos_forks.go

@@ -50,6 +50,12 @@ type RepositoryCreateForkOptions struct {
 
 // CreateFork creates a fork of the specified repository.
 //
+// This method might return an *AcceptedError and a status code of
+// 202. This is because this is the status that GitHub returns to signify that
+// it is now computing creating the fork in a background task.
+// A follow up request, after a delay of a second or so, should result
+// in a successful request.
+//
 // GitHub API docs: https://developer.github.com/v3/repos/forks/#create-a-fork
 func (s *RepositoriesService) CreateFork(owner, repo string, opt *RepositoryCreateForkOptions) (*Repository, *Response, error) {
 	u := fmt.Sprintf("repos/%v/%v/forks", owner, repo)

github/repos_stats.go

@@ -39,8 +39,8 @@ func (w WeeklyStats) String() string {
 // deletions and commit counts.
 //
 // If this is the first time these statistics are requested for the given
-// repository, this method will return a non-nil error and a status code of
-// 202. This is because this is the status that github returns to signify that
+// repository, this method will return an *AcceptedError and a status code of
+// 202. This is because this is the status that GitHub returns to signify that
 // it is now computing the requested statistics. A follow up request, after a
 // delay of a second or so, should result in a successful request.
 //
@@ -78,8 +78,8 @@ func (w WeeklyCommitActivity) String() string {
 // starting on Sunday.
 //
 // If this is the first time these statistics are requested for the given
-// repository, this method will return a non-nil error and a status code of
-// 202. This is because this is the status that github returns to signify that
+// repository, this method will return an *AcceptedError and a status code of
+// 202. This is because this is the status that GitHub returns to signify that
 // it is now computing the requested statistics. A follow up request, after a
 // delay of a second or so, should result in a successful request.
 //
@@ -104,6 +104,12 @@ func (s *RepositoriesService) ListCommitActivity(owner, repo string) ([]*WeeklyC
 // deletions pushed to a repository.  Returned WeeklyStats will contain
 // additions and deletions, but not total commits.
 //
+// If this is the first time these statistics are requested for the given
+// repository, this method will return an *AcceptedError and a status code of
+// 202. This is because this is the status that GitHub returns to signify that
+// it is now computing the requested statistics. A follow up request, after a
+// delay of a second or so, should result in a successful request.
+//
 // GitHub API Docs: https://developer.github.com/v3/repos/statistics/#code-frequency
 func (s *RepositoriesService) ListCodeFrequency(owner, repo string) ([]*WeeklyStats, *Response, error) {
 	u := fmt.Sprintf("repos/%v/%v/stats/code_frequency", owner, repo)
@@ -152,11 +158,10 @@ func (r RepositoryParticipation) String() string {
 // The array order is oldest week (index 0) to most recent week.
 //
 // If this is the first time these statistics are requested for the given
-// repository, this method will return a non-nil error and a status code
-// of 202. This is because this is the status that github returns to
-// signify that it is now computing the requested statistics. A follow
-// up request, after a delay of a second or so, should result in a
-// successful request.
+// repository, this method will return an *AcceptedError and a status code of
+// 202. This is because this is the status that GitHub returns to signify that
+// it is now computing the requested statistics. A follow up request, after a
+// delay of a second or so, should result in a successful request.
 //
 // GitHub API Docs: https://developer.github.com/v3/repos/statistics/#participation
 func (s *RepositoriesService) ListParticipation(owner, repo string) (*RepositoryParticipation, *Response, error) {
@@ -185,6 +190,12 @@ type PunchCard struct {
 
 // ListPunchCard returns the number of commits per hour in each day.
 //
+// If this is the first time these statistics are requested for the given
+// repository, this method will return an *AcceptedError and a status code of
+// 202. This is because this is the status that GitHub returns to signify that
+// it is now computing the requested statistics. A follow up request, after a
+// delay of a second or so, should result in a successful request.
+//
 // GitHub API Docs: https://developer.github.com/v3/repos/statistics/#punch-card
 func (s *RepositoriesService) ListPunchCard(owner, repo string) ([]*PunchCard, *Response, error) {
 	u := fmt.Sprintf("repos/%v/%v/stats/punch_card", owner, repo)