fix: Reject empty search queries with validation (Issue #175)

src/dacli/cli.py

@@ -451,6 +451,11 @@ def sections_at_level(ctx: CliContext, level: int):
 @pass_context
 def search(ctx: CliContext, query: str, scope: str | None, max_results: int):
     """Search for content in the documentation."""
+    # Validate query is not empty
+    if not query or not query.strip():
+        click.echo("Error: Search query cannot be empty", err=True)
+        sys.exit(EXIT_INVALID_ARGS)
+
     results = ctx.index.search(
         query=query,
         scope=scope,

src/dacli/mcp_app.py

@@ -240,7 +240,14 @@ def search(
         Returns:
             Search results with 'query', 'results' (list of matches with
             path, line, context, score), and 'total_results'.
+
+        Raises:
+            ValueError: If query is empty or whitespace-only.
         """
+        # Validate query is not empty
+        if not query or not query.strip():
+            raise ValueError("Search query cannot be empty")
+
         results = index.search(
             query=query,
             scope=scope,

tests/test_cli.py

@@ -314,6 +314,32 @@ def test_search_max_results_still_works(self, sample_docs):
         data = json.loads(result.output)
         assert len(data["results"]) <= 1
 
+    def test_search_empty_query_returns_error(self, sample_docs):
+        """search command should reject empty query with exit code 2."""
+        from dacli.cli import cli
+
+        runner = CliRunner()
+        result = runner.invoke(
+            cli,
+            ["--docs-root", str(sample_docs), "search", ""],
+        )
+
+        assert result.exit_code == 2  # EXIT_INVALID_ARGS
+        assert "Error: Search query cannot be empty" in result.output
+
+    def test_search_whitespace_only_query_returns_error(self, sample_docs):
+        """search command should reject whitespace-only query with exit code 2."""
+        from dacli.cli import cli
+
+        runner = CliRunner()
+        result = runner.invoke(
+            cli,
+            ["--docs-root", str(sample_docs), "search", "   "],
+        )
+
+        assert result.exit_code == 2  # EXIT_INVALID_ARGS
+        assert "Error: Search query cannot be empty" in result.output
+
 
 class TestCliMetadataCommand:
     """Test the 'metadata' command."""

tests/test_mcp_tools.py

@@ -9,6 +9,7 @@
 import pytest
 import pytest_asyncio
 from fastmcp.client import Client
+from fastmcp.exceptions import ToolError
 
 from dacli.mcp_app import create_mcp_server
 
@@ -214,6 +215,16 @@ async def test_search_with_max_results(self, mcp_client: Client):
 
         assert len(result.data["results"]) <= 1
 
+    async def test_search_empty_query_raises_error(self, mcp_client: Client):
+        """search should raise ToolError for empty query."""
+        with pytest.raises(ToolError, match="Search query cannot be empty"):
+            await mcp_client.call_tool("search", arguments={"query": ""})
+
+    async def test_search_whitespace_query_raises_error(self, mcp_client: Client):
+        """search should raise ToolError for whitespace-only query."""
+        with pytest.raises(ToolError, match="Search query cannot be empty"):
+            await mcp_client.call_tool("search", arguments={"query": "   "})
+
 
 class TestGetElements:
     """Tests for get_elements tool."""