feat: support relative paths (#83)

Closes #76

### Summary of Changes

The `cwd` of the worker process can now be set via the new `data.cwd`
item of the `program` message.

---------

Co-authored-by: megalinter-bot <[email protected]>

src/safeds_runner/__init__.py

@@ -1,8 +1,15 @@
 """A runner for the Python code generated from Safe-DS programs."""
 
-from .server._pipeline_manager import file_mtime, memoized_dynamic_call, memoized_static_call, save_placeholder
+from .server._pipeline_manager import (
+    absolute_path,
+    file_mtime,
+    memoized_dynamic_call,
+    memoized_static_call,
+    save_placeholder,
+)
 
 __all__ = [
+    "absolute_path",
     "file_mtime",
     "memoized_static_call",
     "memoized_dynamic_call",

src/safeds_runner/server/_messages.py

@@ -87,10 +87,13 @@ class MessageDataProgram:
         module name. The values of the inner dictionary is the python code for each module.
     main : ProgramMainInformation
         Information where the main pipeline (the pipeline to be executed) is located.
+    cwd:
+        Current working directory to use for execution. If not set, the default working directory is used.
     """
 
     code: dict[str, dict[str, str]]
     main: ProgramMainInformation
+    cwd: str | None = None
 
     @staticmethod
     def from_dict(d: dict[str, Any]) -> MessageDataProgram:
@@ -107,7 +110,11 @@ def from_dict(d: dict[str, Any]) -> MessageDataProgram:
         MessageDataProgram
             Dataclass which contains information copied from the provided dictionary.
         """
-        return MessageDataProgram(d["code"], ProgramMainInformation.from_dict(d["main"]))
+        return MessageDataProgram(
+            d["code"],
+            ProgramMainInformation.from_dict(d["main"]),
+            d.get("cwd"),
+        )
 
     def to_dict(self) -> dict[str, Any]:
         """
@@ -400,7 +407,10 @@ def validate_program_message_data(message_data: dict[str, Any] | str) -> tuple[M
     """
     if not isinstance(message_data, dict):
         return None, "Message data is not a JSON object"
-    elif "code" not in message_data:
+
+    cwd = message_data.get("cwd", None)
+
+    if "code" not in message_data:
         return None, "No 'code' parameter given"
     elif "main" not in message_data:
         return None, "No 'main' parameter given"
@@ -414,6 +424,8 @@ def validate_program_message_data(message_data: dict[str, Any] | str) -> tuple[M
         return None, "Invalid 'main' parameter given"
     elif not isinstance(message_data["code"], dict):
         return None, "Invalid 'code' parameter given"
+    elif cwd is not None and not isinstance(cwd, str):
+        return None, "Invalid 'cwd' parameter given"
     else:
         code: dict = message_data["code"]
         for key in code:

src/safeds_runner/server/_pipeline_manager.py

@@ -4,6 +4,7 @@
 import json
 import logging
 import multiprocessing
+import os
 import queue
 import runpy
 import threading
@@ -265,6 +266,10 @@ def _execute(self) -> None:
         main_module = f"gen_{self._pipeline.main.module}_{self._pipeline.main.pipeline}"
         # Populate current_pipeline global, so child process can save placeholders in correct location
         globals()["current_pipeline"] = self
+
+        if self._pipeline.cwd is not None:
+            os.chdir(self._pipeline.cwd)  # pragma: no cover
+
         try:
             runpy.run_module(
                 (
@@ -408,6 +413,23 @@ def file_mtime(filename: str) -> int | None:
         return None
 
 
+def absolute_path(filename: str) -> str:
+    """
+    Get the absolute path of the provided file.
+
+    Parameters
+    ----------
+    filename:
+        Name of the file
+
+    Returns
+    -------
+    absolute_path:
+        Absolute path of the provided file
+    """
+    return str(Path(filename).resolve())
+
+
 def get_backtrace_info(error: BaseException) -> list[dict[str, Any]]:
     """
     Create a simplified backtrace from an exception.

tests/safeds_runner/server/test_memoization.py

@@ -3,6 +3,7 @@
 import time
 import typing
 from datetime import UTC, datetime
+from pathlib import Path
 from queue import Queue
 from typing import Any
 
@@ -17,6 +18,7 @@
 from safeds_runner.server._messages import MessageDataProgram, ProgramMainInformation
 from safeds_runner.server._pipeline_manager import (
     PipelineProcess,
+    absolute_path,
     file_mtime,
     memoized_dynamic_call,
     memoized_static_call,
@@ -268,6 +270,11 @@ def test_file_mtime_not_exists() -> None:
     assert mtime is None
 
 
+def test_absolute_path() -> None:
+    result = absolute_path("table.csv")
+    assert Path(result).is_absolute()
+
+
 @pytest.mark.parametrize(
     argnames="value,expected_size",
     argvalues=[

tests/safeds_runner/server/test_websocket_mock.py

@@ -284,6 +284,20 @@ def test_should_fail_message_validation_reason_general(websocket_message: str, e
             ),
             "Invalid 'code' parameter given",
         ),
+        (
+            json.dumps(
+                {
+                    "type": "program",
+                    "id": "1234",
+                    "data": {
+                        "code": {},
+                        "main": {"modulepath": "1", "module": "2", "pipeline": "3"},
+                        "cwd": 1,
+                    },
+                },
+            ),
+            "Invalid 'cwd' parameter given",
+        ),
     ],
     ids=[
         "program_invalid_data",
@@ -297,6 +311,7 @@ def test_should_fail_message_validation_reason_general(websocket_message: str, e
         "program_invalid_code1",
         "program_invalid_code2",
         "program_invalid_code3",
+        "program_invalid_cwd",
     ],
 )
 def test_should_fail_message_validation_reason_program(websocket_message: str, exception_message: str) -> None: