Return rate limit information immediately after checkRateLimitBeforeDo (google#572)

Return rate limit information immediately after checkRateLimitBeforeDo

Fixes google#571.

Author: gmlewis

README.md

@@ -82,11 +82,10 @@ limited to 60 requests per hour, while authenticated clients can make up to
 that are not issued on behalf of a user, use the
 `UnauthenticatedRateLimitedTransport`.
 
-The `Rate` method on a client returns the rate limit information based on the most
-recent API call. This is updated on every call, but may be out of date if it's
-been some time since the last API call and other clients have made subsequent
-requests since then. You can always call `RateLimits()` directly to get the most
-up-to-date rate limit data for the client.
+The returned `Response.Rate` value contains the rate limit information
+from the most recent API call. If a recent enough response isn't
+available, you can use `RateLimits` to fetch the most up-to-date rate
+limit data for the client.
 
 To detect an API rate limit error, you can check if its type is `*github.RateLimitError`:
 

github/doc.go

@@ -71,11 +71,10 @@ limited to 60 requests per hour, while authenticated clients can make up to
 that are not issued on behalf of a user, use the
 UnauthenticatedRateLimitedTransport.
 
-The Rate method on a client returns the rate limit information based on the most
-recent API call. This is updated on every call, but may be out of date if it's
-been some time since the last API call and other clients have made subsequent
-requests since then. You can always call RateLimits() directly to get the most
-up-to-date rate limit data for the client.
+The returned Response.Rate value contains the rate limit information
+from the most recent API call. If a recent enough response isn't
+available, you can use RateLimits to fetch the most up-to-date rate
+limit data for the client.
 
 To detect an API rate limit error, you can check if its type is *github.RateLimitError:
 

github/github.go

@@ -396,7 +396,10 @@ func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*Res
 
 	// If we've hit rate limit, don't make further requests before Reset time.
 	if err := c.checkRateLimitBeforeDo(req, rateLimitCategory); err != nil {
-		return nil, err
+		return &Response{
+			Response: err.Response,
+			Rate:     err.Rate,
+		}, err
 	}
 
 	resp, err := c.client.Do(req)
@@ -457,7 +460,7 @@ func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*Res
 // 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 it returns nil, and Client.Do should proceed normally.
-func (c *Client) checkRateLimitBeforeDo(req *http.Request, rateLimitCategory rateLimitCategory) error {
+func (c *Client) checkRateLimitBeforeDo(req *http.Request, rateLimitCategory rateLimitCategory) *RateLimitError {
 	c.rateMu.Lock()
 	rate := c.rateLimits[rateLimitCategory]
 	c.rateMu.Unlock()