Add chunk reading functionality to FileReadTool (#266)

* Add chunk reading functionality to FileReadTool

- Added start_line parameter to specify which line to start reading from
- Added line_count parameter to specify how many lines to read
- Updated documentation with new parameters and examples

* [FIX] Bugs and Disscutions

Fixed: start_line negative value
Improved: File Reading Operations

* [IMPROVE] Simplify line selection

* [REFACTOR] use mock_open while preserving essential filesystem tests

tests/file_read_tool_test.py

@@ -1,4 +1,5 @@
 import os
+from unittest.mock import mock_open, patch
 
 from crewai_tools import FileReadTool
 
@@ -22,19 +23,15 @@ def test_file_read_tool_constructor():
 
 def test_file_read_tool_run():
     """Test FileReadTool _run method with file_path at runtime."""
-    # Create a temporary test file
     test_file = "/tmp/test_file.txt"
     test_content = "Hello, World!"
-    with open(test_file, "w") as f:
-        f.write(test_content)
 
-    # Test reading file with runtime file_path
-    tool = FileReadTool()
-    result = tool._run(file_path=test_file)
-    assert result == test_content
-
-    # Clean up
-    os.remove(test_file)
+    # Use mock_open to mock file operations
+    with patch("builtins.open", mock_open(read_data=test_content)):
+        # Test reading file with runtime file_path
+        tool = FileReadTool()
+        result = tool._run(file_path=test_file)
+        assert result == test_content
 
 
 def test_file_read_tool_error_handling():
@@ -48,41 +45,116 @@ def test_file_read_tool_error_handling():
     result = tool._run(file_path="/nonexistent/file.txt")
     assert "Error: File not found at path:" in result
 
-    # Test permission error (create a file without read permissions)
-    test_file = "/tmp/no_permission.txt"
-    with open(test_file, "w") as f:
-        f.write("test")
-    os.chmod(test_file, 0o000)
-
-    result = tool._run(file_path=test_file)
-    assert "Error: Permission denied" in result
-
-    # Clean up
-    os.chmod(test_file, 0o666)  # Restore permissions to delete
-    os.remove(test_file)
+    # Test permission error
+    with patch("builtins.open", side_effect=PermissionError()):
+        result = tool._run(file_path="/tmp/no_permission.txt")
+        assert "Error: Permission denied" in result
 
 
 def test_file_read_tool_constructor_and_run():
     """Test FileReadTool using both constructor and runtime file paths."""
-    # Create two test files
     test_file1 = "/tmp/test1.txt"
     test_file2 = "/tmp/test2.txt"
     content1 = "File 1 content"
     content2 = "File 2 content"
 
-    with open(test_file1, "w") as f1, open(test_file2, "w") as f2:
-        f1.write(content1)
-        f2.write(content2)
+    # First test with content1
+    with patch("builtins.open", mock_open(read_data=content1)):
+        tool = FileReadTool(file_path=test_file1)
+        result = tool._run()
+        assert result == content1
 
-    # Test that constructor file_path works
-    tool = FileReadTool(file_path=test_file1)
-    result = tool._run()
-    assert result == content1
+    # Then test with content2 (should override constructor file_path)
+    with patch("builtins.open", mock_open(read_data=content2)):
+        result = tool._run(file_path=test_file2)
+        assert result == content2
 
-    # Test that runtime file_path overrides constructor
-    result = tool._run(file_path=test_file2)
-    assert result == content2
 
-    # Clean up
-    os.remove(test_file1)
-    os.remove(test_file2)
+def test_file_read_tool_chunk_reading():
+    """Test FileReadTool reading specific chunks of a file."""
+    test_file = "/tmp/multiline_test.txt"
+    lines = [
+        "Line 1\n",
+        "Line 2\n",
+        "Line 3\n",
+        "Line 4\n",
+        "Line 5\n",
+        "Line 6\n",
+        "Line 7\n",
+        "Line 8\n",
+        "Line 9\n",
+        "Line 10\n",
+    ]
+    file_content = "".join(lines)
+
+    with patch("builtins.open", mock_open(read_data=file_content)):
+        tool = FileReadTool()
+
+        # Test reading a specific chunk (lines 3-5)
+        result = tool._run(file_path=test_file, start_line=3, line_count=3)
+        expected = "".join(lines[2:5])  # Lines are 0-indexed in the array
+        assert result == expected
+
+        # Test reading from a specific line to the end
+        result = tool._run(file_path=test_file, start_line=8)
+        expected = "".join(lines[7:])
+        assert result == expected
+
+        # Test with default values (should read entire file)
+        result = tool._run(file_path=test_file)
+        expected = "".join(lines)
+        assert result == expected
+
+        # Test when start_line is 1 but line_count is specified
+        result = tool._run(file_path=test_file, start_line=1, line_count=5)
+        expected = "".join(lines[0:5])
+        assert result == expected
+
+
+def test_file_read_tool_chunk_error_handling():
+    """Test error handling for chunk reading."""
+    test_file = "/tmp/short_test.txt"
+    lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
+    file_content = "".join(lines)
+
+    with patch("builtins.open", mock_open(read_data=file_content)):
+        tool = FileReadTool()
+
+        # Test start_line exceeding file length
+        result = tool._run(file_path=test_file, start_line=10)
+        assert "Error: Start line 10 exceeds the number of lines in the file" in result
+
+        # Test reading partial chunk when line_count exceeds available lines
+        result = tool._run(file_path=test_file, start_line=2, line_count=10)
+        expected = "".join(lines[1:])  # Should return from line 2 to end
+        assert result == expected
+
+
+def test_file_read_tool_zero_or_negative_start_line():
+    """Test that start_line values of 0 or negative read from the start of the file."""
+    test_file = "/tmp/negative_test.txt"
+    lines = ["Line 1\n", "Line 2\n", "Line 3\n", "Line 4\n", "Line 5\n"]
+    file_content = "".join(lines)
+
+    with patch("builtins.open", mock_open(read_data=file_content)):
+        tool = FileReadTool()
+
+        # Test with start_line = 0
+        result = tool._run(file_path=test_file, start_line=0)
+        expected = "".join(lines)  # Should read the entire file
+        assert result == expected
+
+        # Test with start_line = 0 and limited line count
+        result = tool._run(file_path=test_file, start_line=0, line_count=3)
+        expected = "".join(lines[0:3])  # Should read first 3 lines
+        assert result == expected
+
+        # Test with negative start_line
+        result = tool._run(file_path=test_file, start_line=-5)
+        expected = "".join(lines)  # Should read the entire file
+        assert result == expected
+
+        # Test with negative start_line and limited line count
+        result = tool._run(file_path=test_file, start_line=-10, line_count=2)
+        expected = "".join(lines[0:2])  # Should read first 2 lines
+        assert result == expected