Method checkRateLimitBeforeDo

github/github.go:1355–1390

checkRateLimitBeforeDo does not make any network calls, but uses existing knowledge from current client state in order to quickly check if *RateLimitError can be immediately returned from Client.Do, and if so, returns it so that Client.Do can skip making a network API call unnecessarily. Otherwise i

(req *http.Request, rateLimitCategory RateLimitCategory)

// from Client.Do, and if so, returns it so that Client.Do can skip making a network API call unnecessarily.
// Otherwise it returns nil, and Client.Do should proceed normally.
func (c *Client) checkRateLimitBeforeDo(req *http.Request, rateLimitCategory RateLimitCategory) *RateLimitError {
	ctx := req.Context()

	c.rateMu.Lock()
	rate := c.rateLimits[rateLimitCategory]
	c.rateMu.Unlock()
	if !rate.Reset.Time.IsZero() && rate.Remaining == 0 && time.Now().Before(rate.Reset.Time) {
		// Create a fake response.
		resp := &http.Response{
			Status:     http.StatusText(http.StatusForbidden),
			StatusCode: http.StatusForbidden,
			Request:    req,
			Header:     make(http.Header),
			Body:       io.NopCloser(strings.NewReader("")),
		}

		if ctx.Value(SleepUntilPrimaryRateLimitResetWhenRateLimited) != nil {
			if err := sleepUntilResetWithBuffer(ctx, rate.Reset.Time); err == nil {
				return nil
			}
			return &RateLimitError{
				Rate:     rate,
				Response: resp,
				Message:  fmt.Sprintf("Context cancelled while waiting for rate limit to reset until %v, not making remote request.", rate.Reset.Time),
			}
		}

		return &RateLimitError{
			Rate:     rate,
			Response: resp,
			Message:  fmt.Sprintf("API rate limit of %v still exceeded until %v, not making remote request.", rate.Limit, rate.Reset.Time),
		}
	}

	return nil
}

// checkSecondaryRateLimitBeforeDo does not make any network calls, but uses existing knowledge from
// current client state in order to quickly check if *AbuseRateLimitError can be immediately returned