Filter out blank responses (#270)

* I'm observing cases where we have a non empty suggested cell which
ends up getting deleted.
* It looks like this happens for one of two reasons
* The model responses with an empty code block which doesn't get
filtered out
  * We return a response with no blocks in it

* We should filter these out.
* This means we bias towards generating irrelvant suggestions rather
than no suggestions.
* Right now I think this is helpful because otherwise people might get
confused and wonder whether Foyle is working.

Here's the supporting notebook
https://gist.github.com/jlewi/31857545ec62b36d2949ccd904918d53

app/pkg/agent/agent.go

@@ -244,6 +244,11 @@ func (a *Agent) StreamGenerate(ctx context.Context, stream *connect.BidiStream[v
  return
  }
 
+ if dropResponse(response) {
+ log.V(logs.Debug).Info("Dropping response", zap.Object("response", response))
+ continue
+ }
+
  log.V(logs.Debug).Info("Sending response", zap.Object("response", response))
  if err := stream.Send(response); err != nil {
  log.Error(err, "Failed to send response")
@@ -564,6 +569,11 @@ func postProcessBlocks(blocks []*v1alpha1.Block) ([]*v1alpha1.Block, error) {
  if isOutputTag(block.Contents) {
  continue
  }
+
+ // If the block is empty filter it out.
+ if strings.TrimSpace(block.Contents) == "" {
+ continue
+ }
  results = append(results, block)
  return results, nil
  }
@@ -607,3 +617,17 @@ func shouldTrigger(doc *v1alpha1.Doc, selectedIndex int32) bool {
  selectedCell := doc.Blocks[selectedIndex]
  return selectedCell.GetKind() == v1alpha1.BlockKind_MARKUP
 }
+
+// dropResponse returns true if the response should be dropped rather than being sent to the client.
+// The reason for doing this is because if a previous generation generated a "good" response we don't want
+// to overwrite it with this one
+func dropResponse(response *v1alpha1.StreamGenerateResponse) bool {
+ if response == nil {
+ return true
+ }
+ // We don't want to send empty cells because that will cause the client to remove any previously suggested cells
+ if len(response.Cells) == 0 {
+ return true
+ }
+ return false
+}

app/pkg/agent/agent_test.go

@@ -361,6 +361,16 @@ func Test_PostProcessBlocks(t *testing.T) {
  },
  expected: []*v1alpha1.Block{},
  },
+ {
+ name: "whitespace-only-block",
+ blocks: []*v1alpha1.Block{
+ {
+ Kind: v1alpha1.BlockKind_CODE,
+ Contents: " ",
+ },
+ },
+ expected: []*v1alpha1.Block{},
+ },
  }
 
  for _, c := range cases {
@@ -375,3 +385,42 @@ func Test_PostProcessBlocks(t *testing.T) {
  })
  }
 }
+
+func Test_dropResponse(t *testing.T) {
+ type testCase struct {
+ name string
+ response *v1alpha1.StreamGenerateResponse
+ expected bool
+ }
+
+ cases := []testCase{
+ {
+ name: "basic",
+ response: &v1alpha1.StreamGenerateResponse{
+ Cells: []*parserv1.Cell{
+ {
+ Kind: parserv1.CellKind_CELL_KIND_CODE,
+ Value: "print('Hello, World!')",
+ },
+ },
+ },
+ expected: false,
+ },
+ {
+ name: "empty",
+ response: &v1alpha1.StreamGenerateResponse{
+ Cells: []*parserv1.Cell{},
+ },
+ expected: true,
+ },
+ }
+
+ for _, c := range cases {
+ t.Run(c.name, func(t *testing.T) {
+ result := dropResponse(c.response)
+ if result != c.expected {
+ t.Errorf("Expected %v; got %v", c.expected, result)
+ }
+ })
+ }
+}