fix: error on invalid v1 config docs (#2993)

## Summary
- return hard errors for invalid v1 docs in ConvertConfig (no silent
drop)
- include doc index + key path + v2 hint in error
- add tests for invalid v1 docs
## Testing
   - go test ./cmd/internal -run TestConvertConfig      
 fixes #2926

---------

Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com>

Author: Deeven-Seru

cmd/internal/config.go

@@ -128,17 +128,19 @@ func ConvertConfig(raw []byte) ([]byte, error) {
 	encoder := yaml.NewEncoder(&buf)
 
 	v1keys := []string{"sources", "authServices", "embeddingModels", "tools", "toolsets", "prompts"}
+	docIndex := 0
 	for {
 		if err := decoder.Decode(&input); err != nil {
 			if err == io.EOF {
 				break
 			}
 			return nil, err
 		}
+		docIndex++
 		for _, item := range input {
 			key, ok := item.Key.(string)
 			if !ok {
-				return nil, fmt.Errorf("unexpected non-string key in input: %v", item.Key)
+				return nil, fmt.Errorf("doc %d: unexpected non-string key in input: %v", docIndex, item.Key)
 			}
 			// check if the key is config file v1's key
 			if slices.Contains(v1keys, key) {
@@ -163,7 +165,7 @@ func ConvertConfig(raw []byte) ([]byte, error) {
 					}
 					transformed, err := transformDocs(key, slice)
 					if err != nil {
-						return nil, err
+						return nil, fmt.Errorf("doc %d: invalid config format at key %q: %w", docIndex, key, err)
 					}
 					// encode per-doc
 					for _, doc := range transformed {
@@ -172,15 +174,14 @@ func ConvertConfig(raw []byte) ([]byte, error) {
 						}
 					}
 				} else {
-					// invalid input will be ignored
-					// we don't want to throw error here since the config could
-					// be valid but with a different order such as:
-					// ---
-					// tools:
-					// - tool_a
-					// kind: toolset
-					// ---
-					continue
+					if hasKindField(input) {
+						// this doc is already v2, encode to buf
+						if err := encoder.Encode(input); err != nil {
+							return nil, err
+						}
+						break
+					}
+					return nil, fmt.Errorf("doc %d: invalid config format at key %q: expected map", docIndex, key)
 				}
 			} else {
 				// this doc is already v2, encode to buf
@@ -194,6 +195,15 @@ func ConvertConfig(raw []byte) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+func hasKindField(input yaml.MapSlice) bool {
+	for _, item := range input {
+		if key, ok := item.Key.(string); ok && key == "kind" {
+			return true
+		}
+	}
+	return false
+}
+
 // transformDocs transforms the configuration file from v1 format to v2
 // yaml.MapSlice will preserve the order in a map
 func transformDocs(kind string, input yaml.MapSlice) ([]yaml.MapSlice, error) {

cmd/internal/config_test.go

@@ -531,19 +531,30 @@ tools:
 `,
 		},
 		{
-			desc: "invalid source",
-			in:   `sources: invalid`,
-			want: "",
+			desc:   "invalid source",
+			in:     `sources: invalid`,
+			isErr:  true,
+			errStr: `doc 1: invalid config format at key "sources": expected map`,
 		},
 		{
-			desc: "invalid toolset",
-			in:   `toolsets: invalid`,
-			want: "",
+			desc:   "invalid toolset",
+			in:     `toolsets: invalid`,
+			isErr:  true,
+			errStr: `doc 1: invalid config format at key "toolsets": expected map`,
 		},
 	}
 	for _, tc := range tcs {
 		t.Run(tc.desc, func(t *testing.T) {
 			output, err := ConvertConfig([]byte(tc.in))
+			if tc.isErr {
+				if err == nil {
+					t.Fatalf("expected error")
+				}
+				if tc.errStr != "" && err.Error() != tc.errStr {
+					t.Fatalf("incorrect error string: got %s, want %s", err, tc.errStr)
+				}
+				return
+			}
 			if err != nil {
 				t.Fatalf("unexpected error: %s", err)
 			}