Add optional string array param

Author: williammartin

Diff for: pkg/github/issues.go

@@ -286,13 +286,13 @@ func createIssue(client *github.Client, t translations.TranslationHelperFunc) (t
 			}
 
 			// Get assignees
-			assignees, err := optionalParam[[]string](request, "assignees")
+			assignees, err := optionalStringArrayParam(request, "assignees")
 			if err != nil {
 				return mcp.NewToolResultError(err.Error()), nil
 			}
 
 			// Get labels
-			labels, err := optionalParam[[]string](request, "labels")
+			labels, err := optionalStringArrayParam(request, "labels")
 			if err != nil {
 				return mcp.NewToolResultError(err.Error()), nil
 			}
@@ -401,7 +401,7 @@ func listIssues(client *github.Client, t translations.TranslationHelperFunc) (to
 			}
 
 			// Get labels
-			opts.Labels, err = optionalParam[[]string](request, "labels")
+			opts.Labels, err = optionalStringArrayParam(request, "labels")
 			if err != nil {
 				return mcp.NewToolResultError(err.Error()), nil
 			}
@@ -548,7 +548,7 @@ func updateIssue(client *github.Client, t translations.TranslationHelperFunc) (t
 			}
 
 			// Get labels
-			labels, err := optionalParam[[]string](request, "labels")
+			labels, err := optionalStringArrayParam(request, "labels")
 			if err != nil {
 				return mcp.NewToolResultError(err.Error()), nil
 			}
@@ -557,7 +557,7 @@ func updateIssue(client *github.Client, t translations.TranslationHelperFunc) (t
 			}
 
 			// Get assignees
-			assignees, err := optionalParam[[]string](request, "assignees")
+			assignees, err := optionalStringArrayParam(request, "assignees")
 			if err != nil {
 				return mcp.NewToolResultError(err.Error()), nil
 			}

Diff for: pkg/github/issues_test.go

@@ -436,8 +436,8 @@ func Test_CreateIssue(t *testing.T) {
 				"repo":      "repo",
 				"title":     "Test Issue",
 				"body":      "This is a test issue",
-				"assignees": []string{"user1", "user2"},
-				"labels":    []string{"bug", "help wanted"},
+				"assignees": []any{"user1", "user2"},
+				"labels":    []any{"bug", "help wanted"},
 				"milestone": float64(5),
 			},
 			expectError:   false,
@@ -636,7 +636,7 @@ func Test_ListIssues(t *testing.T) {
 				"owner":     "owner",
 				"repo":      "repo",
 				"state":     "open",
-				"labels":    []string{"bug", "enhancement"},
+				"labels":    []any{"bug", "enhancement"},
 				"sort":      "created",
 				"direction": "desc",
 				"since":     "2023-01-01T00:00:00Z",
@@ -790,8 +790,8 @@ func Test_UpdateIssue(t *testing.T) {
 				"title":        "Updated Issue Title",
 				"body":         "Updated issue description",
 				"state":        "closed",
-				"labels":       []string{"bug", "priority"},
-				"assignees":    []string{"assignee1", "assignee2"},
+				"labels":       []any{"bug", "priority"},
+				"assignees":    []any{"assignee1", "assignee2"},
 				"milestone":    float64(5),
 			},
 			expectError:   false,

Diff for: pkg/github/server.go

@@ -171,7 +171,7 @@ func optionalParam[T any](r mcp.CallToolRequest, p string) (T, error) {
 
 	// Check if the parameter is of the expected type
 	if _, ok := r.Params.Arguments[p].(T); !ok {
-		return zero, fmt.Errorf("parameter %s is not of type %T", p, zero)
+		return zero, fmt.Errorf("parameter %s is not of type %T, is %T", p, zero, r.Params.Arguments[p])
 	}
 
 	return r.Params.Arguments[p].(T), nil
@@ -201,3 +201,31 @@ func optionalIntParamWithDefault(r mcp.CallToolRequest, p string, d int) (int, e
 	}
 	return v, nil
 }
+
+// optionalStringArrayParam is a helper function that can be used to fetch a requested parameter from the request.
+// It does the following checks:
+// 1. Checks if the parameter is present in the request, if not, it returns its zero-value
+// 2. If it is present, iterates the elements and checks each is a string
+func optionalStringArrayParam(r mcp.CallToolRequest, p string) ([]string, error) {
+	// Check if the parameter is present in the request
+	if _, ok := r.Params.Arguments[p]; !ok {
+		return []string{}, nil
+	}
+
+	switch v := r.Params.Arguments[p].(type) {
+	case []string:
+		return v, nil
+	case []any:
+		strSlice := make([]string, len(v))
+		for i, v := range v {
+			s, ok := v.(string)
+			if !ok {
+				return []string{}, fmt.Errorf("parameter %s is not of type string, is %T", p, v)
+			}
+			strSlice[i] = s
+		}
+		return strSlice, nil
+	default:
+		return []string{}, fmt.Errorf("parameter %s could not be coerced to []string, is %T", p, r.Params.Arguments[p])
+	}
+}

Diff for: pkg/github/server_test.go

@@ -483,3 +483,71 @@ func Test_OptionalBooleanParam(t *testing.T) {
 		})
 	}
 }
+
+func TestOptionalStringArrayParam(t *testing.T) {
+	tests := []struct {
+		name        string
+		params      map[string]interface{}
+		paramName   string
+		expected    []string
+		expectError bool
+	}{
+		{
+			name:        "parameter not in request",
+			params:      map[string]any{},
+			paramName:   "flag",
+			expected:    []string{},
+			expectError: false,
+		},
+		{
+			name: "valid any array parameter",
+			params: map[string]any{
+				"flag": []any{"v1", "v2"},
+			},
+			paramName:   "flag",
+			expected:    []string{"v1", "v2"},
+			expectError: false,
+		},
+		{
+			name: "valid string array parameter",
+			params: map[string]any{
+				"flag": []string{"v1", "v2"},
+			},
+			paramName:   "flag",
+			expected:    []string{"v1", "v2"},
+			expectError: false,
+		},
+		{
+			name: "wrong type parameter",
+			params: map[string]any{
+				"flag": 1,
+			},
+			paramName:   "flag",
+			expected:    []string{},
+			expectError: true,
+		},
+		{
+			name: "wrong slice type parameter",
+			params: map[string]any{
+				"flag": []any{"foo", 2},
+			},
+			paramName:   "flag",
+			expected:    []string{},
+			expectError: true,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			request := createMCPRequest(tc.params)
+			result, err := optionalStringArrayParam(request, tc.paramName)
+
+			if tc.expectError {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tc.expected, result)
+			}
+		})
+	}
+}