Fix Dart LSP hover marshalling issue and add integration tests

The Dart Language Server returns hover contents as plain strings in some cases,
which was causing JSON unmarshalling errors. According to the LSP specification,
the hover contents field can be:
- MarkupContent (object with kind and value)
- MarkedString (plain string)
- MarkedString[] (array of strings or language/value objects)

Changes:
- Fixed code generation to use Or_Hover_contents union type instead of MarkupContent
- Updated hover.go to handle all possible content types from the LSP spec
- Added comprehensive Dart integration tests with 13 test cases
- Added Dart to GitHub Actions CI workflow
- Updated .gitignore for Dart artifacts

This ensures the MCP language server correctly handles all valid hover response
formats from any LSP server, not just those that return MarkupContent objects.

Fixes the issue where Dart hover functionality would fail with:
"json: cannot unmarshal string into Go struct field Hover.contents of type protocol.MarkupContent"

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

.github/workflows/go.yml

@@ -55,6 +55,27 @@ jobs:
       - name: Run Go integration tests
         run: go test ./integrationtests/tests/go/...
 
+  dart-integration-tests:
+    name: Dart Integration Tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"
+          check-latest: true
+          cache: true
+
+      - name: Set up Dart SDK
+        uses: dart-lang/setup-dart@v1
+        with:
+          sdk: stable
+
+      - name: Run Dart integration tests
+        run: go test ./integrationtests/tests/dart/...
+
   python-integration-tests:
     name: Python Integration Tests
     runs-on: ubuntu-latest
@@ -155,7 +176,7 @@ jobs:
           sudo ln -s /usr/bin/clangd-16 /usr/bin/clangd
           clangd-16 --version
           clangd --version
-      
+
       - name: Create compile commands
         run: |
           cd integrationtests/workspaces/clangd

.gitignore

@@ -10,6 +10,11 @@ integrationtests/workspaces/clangd/clean_program
 integrationtests/workspaces/clangd/program
 integrationtests/workspaces/clangd/.cache
 
+# Dart
+.dart_tool/
+*.dart.js
+*.dart.js.map
+
 
 # Temporary files
 *~

cmd/generate/tables.go

@@ -67,7 +67,7 @@ var renameProp = map[prop]string{
 
 	{"ExecuteCommandParams", "arguments"}: "[]json.RawMessage",
 	{"FoldingRange", "kind"}:              "string",
-	{"Hover", "contents"}:                 "MarkupContent",
+	{"Hover", "contents"}:                 "Or_Hover_contents",
 	{"InlayHint", "label"}:                "[]InlayHintLabelPart",
 
 	{"RelatedFullDocumentDiagnosticReport", "relatedDocuments"}:      "map[DocumentUri]interface{}",

integrationtests/snapshots/dart/hover/class-method.snap

@@ -0,0 +1,7 @@
+```dart
+String process()
+```
+*types.dart*
+
+---
+A method that processes the value

integrationtests/snapshots/dart/hover/constant.snap

@@ -0,0 +1,9 @@
+```dart
+String SHARED_CONSTANT
+```
+Type: `String`
+
+*types.dart*
+
+---
+A constant value

integrationtests/snapshots/dart/hover/enum.snap

@@ -0,0 +1,7 @@
+```dart
+enum Color
+```
+*types.dart*
+
+---
+An enum for testing

integrationtests/snapshots/dart/hover/function.snap

@@ -0,0 +1,7 @@
+```dart
+HelperClass createHelper(String name)
+```
+*helper.dart*
+
+---
+A helper function that creates instances

integrationtests/snapshots/dart/hover/global-variable.snap

@@ -0,0 +1,9 @@
+```dart
+HelperClass globalHelper
+```
+Type: `HelperClass`
+
+*helper.dart*
+
+---
+Global variable for testing

integrationtests/snapshots/dart/hover/helper-class.snap

@@ -0,0 +1,7 @@
+```dart
+class HelperClass implements SharedInterface
+```
+*helper.dart*
+
+---
+Helper class for demonstration

integrationtests/snapshots/dart/hover/interface.snap

@@ -0,0 +1,7 @@
+```dart
+abstract class SharedInterface
+```
+*types.dart*
+
+---
+An interface for testing

integrationtests/snapshots/dart/hover/main-function.snap

@@ -0,0 +1,4 @@
+```dart
+void main()
+```
+*main.dart*

integrationtests/snapshots/dart/hover/no-hover-info.snap

@@ -0,0 +1,2 @@
+No hover information available for this position on the following line:
+// Main test file for Dart hover tests

integrationtests/snapshots/dart/hover/override-method.snap

@@ -0,0 +1,4 @@
+```dart
+void doSomething()
+```
+*helper.dart*

integrationtests/snapshots/dart/hover/shared-class.snap

@@ -0,0 +1,8 @@
+```dart
+class SharedClass
+```
+*types.dart*
+
+---
+A shared class used across multiple files
+This class demonstrates hover information

integrationtests/snapshots/dart/hover/type-alias.snap

@@ -0,0 +1,7 @@
+```dart
+typedef ProcessFunction = String Function(int )
+```
+*types.dart*
+
+---
+A type alias for testing

integrationtests/snapshots/dart/hover/variable.snap

@@ -0,0 +1,4 @@
+```dart
+InvalidType helper
+```
+Type: `InvalidType`

integrationtests/tests/dart/hover/hover_test.go

@@ -0,0 +1,179 @@
+package hover_test
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/isaacphi/mcp-language-server/integrationtests/tests/common"
+	"github.com/isaacphi/mcp-language-server/integrationtests/tests/dart/internal"
+	"github.com/isaacphi/mcp-language-server/internal/tools"
+)
+
+// TestHover tests hover functionality with the Dart language server
+func TestHover(t *testing.T) {
+	tests := []struct {
+		name           string
+		file           string
+		line           int
+		column         int
+		expectedText   string // Text that should be in the hover result
+		unexpectedText string // Text that should NOT be in the hover result (optional)
+		snapshotName   string
+	}{
+		// Tests using types.dart file
+		{
+			name:         "SharedClass",
+			file:         "types.dart",
+			line:         5,
+			column:       7,
+			expectedText: "SharedClass",
+			snapshotName: "shared-class",
+		},
+		{
+			name:         "ClassMethod",
+			file:         "types.dart",
+			line:         15,
+			column:       10,
+			expectedText: "process",
+			snapshotName: "class-method",
+		},
+		{
+			name:         "Interface",
+			file:         "types.dart",
+			line:         21,
+			column:       16,
+			expectedText: "SharedInterface",
+			snapshotName: "interface",
+		},
+		{
+			name:         "TypeAlias",
+			file:         "types.dart",
+			line:         27,
+			column:       9,
+			expectedText: "ProcessFunction",
+			snapshotName: "type-alias",
+		},
+		{
+			name:         "Constant",
+			file:         "types.dart",
+			line:         30,
+			column:       14,
+			expectedText: "SHARED_CONSTANT",
+			snapshotName: "constant",
+		},
+		{
+			name:         "Enum",
+			file:         "types.dart",
+			line:         33,
+			column:       6,
+			expectedText: "Color",
+			snapshotName: "enum",
+		},
+		// Tests using helper.dart file
+		{
+			name:         "HelperClass",
+			file:         "helper.dart",
+			line:         4,
+			column:       7,
+			expectedText: "HelperClass",
+			snapshotName: "helper-class",
+		},
+		{
+			name:         "OverrideMethod",
+			file:         "helper.dart",
+			line:         10,
+			column:       8,
+			expectedText: "doSomething",
+			snapshotName: "override-method",
+		},
+		{
+			name:         "Function",
+			file:         "helper.dart",
+			line:         25,
+			column:       14,
+			expectedText: "createHelper",
+			snapshotName: "function",
+		},
+		{
+			name:         "GlobalVariable",
+			file:         "helper.dart",
+			line:         30,
+			column:       7,
+			expectedText: "globalHelper",
+			snapshotName: "global-variable",
+		},
+		// Tests using main.dart file
+		{
+			name:         "MainFunction",
+			file:         "main.dart",
+			line:         5,
+			column:       6,
+			expectedText: "main",
+			snapshotName: "main-function",
+		},
+		{
+			name:         "Variable",
+			file:         "main.dart",
+			line:         8,
+			column:       7,
+			expectedText: "helper",
+			snapshotName: "variable",
+		},
+	}
+
+	suite := internal.GetTestSuite(t)
+
+	// Wait for initialization
+	time.Sleep(time.Duration(suite.Config.InitializeTimeMs) * time.Millisecond)
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			filePath := filepath.Join(suite.WorkspaceDir, tt.file)
+
+			// Get hover information
+			result, err := tools.GetHoverInfo(context.Background(), suite.Client, filePath, tt.line, tt.column)
+			if err != nil {
+				t.Fatalf("Failed to get hover info: %v", err)
+			}
+
+			// Check if expected text is present
+			if tt.expectedText != "" && !strings.Contains(result, tt.expectedText) {
+				t.Errorf("Expected text '%s' not found in hover result: %s", tt.expectedText, result)
+			}
+
+			// Check if unexpected text is absent
+			if tt.unexpectedText != "" && strings.Contains(result, tt.unexpectedText) {
+				t.Errorf("Unexpected text '%s' found in hover result: %s", tt.unexpectedText, result)
+			}
+
+			// Perform snapshot test
+			common.SnapshotTest(t, suite.LanguageName, "hover", tt.snapshotName, result)
+		})
+	}
+}
+
+// TestHoverNoInfo tests hover on positions without hover information
+func TestHoverNoInfo(t *testing.T) {
+	suite := internal.GetTestSuite(t)
+
+	// Wait for initialization
+	time.Sleep(time.Duration(suite.Config.InitializeTimeMs) * time.Millisecond)
+
+	// Test hover on an empty line or comment
+	filePath := filepath.Join(suite.WorkspaceDir, "main.dart")
+	result, err := tools.GetHoverInfo(context.Background(), suite.Client, filePath, 1, 1)
+	if err != nil {
+		t.Fatalf("Failed to get hover info: %v", err)
+	}
+
+	// Should indicate no hover information
+	if !strings.Contains(result, "No hover information") {
+		t.Logf("Result when no hover info expected: %s", result)
+	}
+
+	// Snapshot test for no hover info case
+	common.SnapshotTest(t, suite.LanguageName, "hover", "no-hover-info", result)
+}