feat: add JSON language server support via vscode-json-languageserver (#1404)

* feat: add JSON language server support via vscode-json-languageserver (fixes #1391)

Add support for JSON files using the `vscode-json-languageserver` npm package
from Microsoft. This provides document symbol navigation and hover information
for JSON files.

The implementation follows the existing YAML language server pattern:
- Auto-installs `vscode-json-languageserver` via npm on first use
- Requires Node.js and npm
- Marked as experimental (must be explicitly specified)

Co-Authored-By: Octopus <liyuan851277048@icloud.com>
Co-authored-by: octo-patch <octo-patch@github.com>
Co-authored-by: Michael Panchenko <35432522+MischaPanch@users.noreply.github.com>

test/solidlsp/json_ls/test_json_basic.py

@@ -0,0 +1,78 @@
+"""
+Basic integration tests for the JSON language server functionality.
+
+These tests validate the functionality of the language server APIs
+like request_document_symbols using the JSON test repository.
+"""
+
+from pathlib import Path
+
+import pytest
+
+from solidlsp import SolidLanguageServer
+from solidlsp.ls_config import Language
+from test.solidlsp.conftest import format_symbol_for_assert, has_malformed_name, request_all_symbols
+
+
+@pytest.mark.json
+class TestJsonLanguageServerBasics:
+    """Test basic functionality of the JSON language server."""
+
+    @pytest.mark.parametrize("language_server", [Language.JSON], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.JSON], indirect=True)
+    def test_json_language_server_initialization(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        """Test that JSON language server can be initialized successfully."""
+        assert language_server is not None
+        assert language_server.language == Language.JSON
+        assert language_server.is_running()
+        assert Path(language_server.language_server.repository_root_path).resolve() == repo_path.resolve()
+
+    @pytest.mark.parametrize("language_server", [Language.JSON], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.JSON], indirect=True)
+    def test_json_config_file_symbols(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        """Test document symbols detection in config.json with specific symbol verification."""
+        all_symbols, root_symbols = language_server.request_document_symbols("config.json").get_all_symbols_and_roots()
+
+        assert all_symbols is not None, "Should return symbols for config.json"
+        assert len(all_symbols) > 0, f"Should find symbols in config.json, found {len(all_symbols)}"
+
+        symbol_names = [sym.get("name") for sym in all_symbols]
+        assert "app" in symbol_names, "Should detect 'app' key in config.json"
+        assert "database" in symbol_names, "Should detect 'database' key in config.json"
+        assert "logging" in symbol_names, "Should detect 'logging' key in config.json"
+        assert "features" in symbol_names, "Should detect 'features' key in config.json"
+
+        # Verify nested symbols
+        assert "name" in symbol_names, "Should detect nested 'name' key"
+        assert "port" in symbol_names, "Should detect nested 'port' key"
+        assert "debug" in symbol_names, "Should detect nested 'debug' key"
+
+    @pytest.mark.parametrize("language_server", [Language.JSON], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.JSON], indirect=True)
+    def test_json_data_file_symbols(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        """Test symbol detection in data.json with array structures."""
+        all_symbols, root_symbols = language_server.request_document_symbols("data.json").get_all_symbols_and_roots()
+
+        assert all_symbols is not None, "Should return symbols for data.json"
+        assert len(all_symbols) > 0, f"Should find symbols in data.json, found {len(all_symbols)}"
+
+        symbol_names = [sym.get("name") for sym in all_symbols]
+        assert "users" in symbol_names, "Should detect 'users' array"
+        assert "projects" in symbol_names, "Should detect 'projects' array"
+        assert "name" in symbol_names, "Should detect 'name' fields"
+        assert "email" in symbol_names, "Should detect 'email' fields"
+        assert "id" in symbol_names, "Should detect 'id' fields"
+
+    @pytest.mark.parametrize("language_server", [Language.JSON], indirect=True)
+    def test_bare_symbol_names(self, language_server: SolidLanguageServer) -> None:
+        """Test that symbol names do not contain malformed characters."""
+        all_symbols = request_all_symbols(language_server)
+        malformed_symbols = []
+        for s in all_symbols:
+            if has_malformed_name(s, period_allowed=True):
+                malformed_symbols.append(s)
+        if malformed_symbols:
+            pytest.fail(
+                f"Found malformed symbols: {[format_symbol_for_assert(sym) for sym in malformed_symbols]}",
+                pytrace=False,
+            )