Return same not-found response from dh and non-dh clients (#124)

The Client and DHashClient need to return the same response when no results are found. Return empty response for not found to preserve compatability with clients that expect non-nil response.

Fixes #53

find/client/client.go

@@ -55,15 +55,35 @@ func New(baseURL string, options ...Option) (*Client, error) {
 	}, nil
 }
 
-// Find looks up content entries by multihash.
+// Find looks up content entries by multihash. If no results are found then an
+// empty response without error is returned.
 func (c *Client) Find(ctx context.Context, m multihash.Multihash) (*model.FindResponse, error) {
 	u := c.findURL.JoinPath(m.B58String())
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
 	if err != nil {
 		return nil, err
 	}
 
-	return c.sendRequest(req)
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := c.c.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	// Handle failed requests
+	if resp.StatusCode != http.StatusOK {
+		if resp.StatusCode == http.StatusNotFound {
+			return &model.FindResponse{}, nil
+		}
+		return nil, fmt.Errorf("find query failed: %v", http.StatusText(resp.StatusCode))
+	}
+
+	defer resp.Body.Close()
+	b, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	return model.UnmarshalFindResponse(b)
 }
 
 func (c *Client) ListProviders(ctx context.Context) ([]*model.ProviderInfo, error) {
@@ -154,26 +174,3 @@ func (c *Client) GetStats(ctx context.Context) (*model.Stats, error) {
 
 	return model.UnmarshalStats(body)
 }
-
-func (c *Client) sendRequest(req *http.Request) (*model.FindResponse, error) {
-	req.Header.Set("Content-Type", "application/json")
-	resp, err := c.c.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	// Handle failed requests
-	if resp.StatusCode != http.StatusOK {
-		if resp.StatusCode == http.StatusNotFound {
-			return &model.FindResponse{}, nil
-		}
-		return nil, fmt.Errorf("batch find query failed: %v", http.StatusText(resp.StatusCode))
-	}
-
-	defer resp.Body.Close()
-	b, err := io.ReadAll(resp.Body)
-	if err != nil {
-		return nil, err
-	}
-
-	return model.UnmarshalFindResponse(b)
-}

find/client/dhash_client.go

@@ -98,7 +98,8 @@ func (c *DHashClient) PCache() *pcache.ProviderCache {
 }
 
 // Find launches FindAsync in a separate go routine and assembles the result
-// into FindResponse as if it was a synchronous invocation.
+// into FindResponse as if it was a synchronous invocation. If no results are
+// found then an empty response without error is returned.
 func (c *DHashClient) Find(ctx context.Context, mh multihash.Multihash) (*model.FindResponse, error) {
 	resChan := make(chan model.ProviderResult)
 	errChan := make(chan error, 1)
@@ -107,18 +108,25 @@ func (c *DHashClient) Find(ctx context.Context, mh multihash.Multihash) (*model.
 		errChan <- c.FindAsync(ctx, mh, resChan)
 	}()
 
-	mhr := model.MultihashResult{
-		Multihash: mh,
-	}
+	var providerResults []model.ProviderResult
 	for pr := range resChan {
-		mhr.ProviderResults = append(mhr.ProviderResults, pr)
+		providerResults = append(providerResults, pr)
 	}
 	err := <-errChan
 	if err != nil {
 		return nil, err
 	}
+	if len(providerResults) == 0 {
+		return &model.FindResponse{}, nil
+	}
+
 	return &model.FindResponse{
-		MultihashResults: []model.MultihashResult{mhr},
+		MultihashResults: []model.MultihashResult{
+			{
+				Multihash:       mh,
+				ProviderResults: providerResults,
+			},
+		},
 	}, nil
 }
 

find/client/interface.go

@@ -12,14 +12,14 @@ import (
 
 // Finder is the interface implemented by all find clients.
 type Finder interface {
-	// Find queries for provider content records for a single multihash.
+	// Find queries for provider content records for a single multihash. If no
+	// results are found then an empty response without error is returned.
 	Find(context.Context, multihash.Multihash) (*model.FindResponse, error)
 }
 
 // FindBatch is a convenience function to lookup results for multiple
 // multihashes. This works with either the Client or DHashClient. If no results
-// are found, then an error is not returned and there are no results in the
-// response.
+// are found then an empty response without error is returned.
 func FindBatch(ctx context.Context, finder Finder, mhs []multihash.Multihash) (*model.FindResponse, error) {
 	var resp *model.FindResponse
 	for i := range mhs {
@@ -31,11 +31,18 @@ func FindBatch(ctx context.Context, finder Finder, mhs []multihash.Multihash) (*
 			}
 			return nil, err
 		}
+		if r == nil || len(r.MultihashResults) == 0 {
+			// multihash not found
+			continue
+		}
 		if resp == nil {
 			resp = r
 		} else {
 			resp.MultihashResults = append(resp.MultihashResults, r.MultihashResults...)
 		}
 	}
+	if resp == nil {
+		resp = &model.FindResponse{}
+	}
 	return resp, nil
 }