Lab/py control file (#4420)

* feat: use python's compile for rc.py

* docs: add news item

* docs: update news item

* test: add tests for py-control files

* fix: rst news item

* docs: update news item

* docs: add sample rc.py

docs/xonshrc.py

@@ -0,0 +1,23 @@
+from xonsh.built_ins import XSH
+
+env = XSH.env
+# adjust some paths
+env["PATH"].append("/home/scopatz/sandbox/bin")
+env["LD_LIBRARY_PATH"] = ["/home/scopatz/.local/lib", "/home/scopatz/miniconda3/lib"]
+
+# alias to quit AwesomeWM from the terminal
+def _quit_awesome(args, stdin=None):
+    print("awesome python code")
+
+
+XSH.aliases["qa"] = _quit_awesome
+# setting aliases as list are faster since they don't involve parser.
+XSH.aliases["gc"] = ["git", "commit"]
+
+# some customization options, see https://xon.sh/envvars.html for details
+env["MULTILINE_PROMPT"] = "`·.,¸,.·*¯`·.,¸,.·*¯"
+env["XONSH_SHOW_TRACEBACK"] = True
+env["XONSH_STORE_STDOUT"] = True
+env["XONSH_HISTORY_MATCH_ANYWHERE"] = True
+env["COMPLETIONS_CONFIRM"] = True
+env["XONSH_AUTOPAIR"] = True

docs/xonshrc.rst

@@ -1,7 +1,9 @@
 Run Control File
 =========================
 Xonsh allows you to customize your shell behavior with run control files, called "xonshrc" files.  
-These files are written in the xonsh language (a superset of Python) and are executed exactly once at startup.   
+These files are written either in the Xonsh language (a superset of Python) or in Python and are executed
+exactly once at startup.
+
 The control file usually contains:
 
 * Assignment statements setting `environment variables <envvars.html>`_.  This includes standard OS environment variables that affect other programs and many that Xonsh uses for itself.
@@ -19,7 +21,7 @@ The options set per user override settings in the system-wide control file.
 Xonsh also supports configuration directories, from which all ``.xsh`` files will be sourced in order.
 This allows for drop-in configuration where your configuration can be split across scripts and common
 and local configuration more easily separated. By default, if the directory ``~/.config/xonsh/rc.d``
-exists, any ``xsh`` files within will be sourced at startup.
+exists, any ``*.xsh`` files within will be sourced at startup.
 
 Xonsh provides 2 wizards to create your own "xonshrc".  ``xonfig web`` provides basic settings, and ``xonfig wizard``
 steps you through all the available options.
@@ -167,6 +169,18 @@ The following is a real-world example of such a file.
     :code: xonsh
 
 
+Real world sample rc.py
+-------------------------
+
+The following is a real-world example of such a file.
+This can be set by ``env XONSHRC=rc.py xonsh`` or ``xonsh --rc=rc.py``
+
+:download:`Download rc.py <xonshrc.py>`
+
+.. include:: xonshrc.py
+    :code: xonsh
+
+
 Snippets for xonshrc
 --------------------
 

news/py-rc-files.rst

@@ -0,0 +1,24 @@
+**Added:**
+
+* Pure Python control files are now supported when named ``*.py``.
+  Using python files may lower the startup time by a bit.
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

requirements/tests.txt

@@ -5,6 +5,7 @@ flake8-docstrings
 flake8-bugbear
 restructuredtext_lint
 pytest-cov
+pytest-mock
 pytest-timeout
 pytest-subprocess
 prompt-toolkit>=3.0

tests/test_main.py

@@ -12,7 +12,7 @@ import sys
 import xonsh.main
 from xonsh.main import XonshMode
 import pytest
-from tools import ON_WINDOWS, TEST_DIR, VER_FULL, skip_if_on_windows
+from tools import ON_WINDOWS, TEST_DIR, skip_if_on_windows
 
 
 def Shell(*args, **kwargs):
@@ -90,6 +90,30 @@ def test_rc_with_modules(shell, tmpdir, monkeypatch, capsys, xession):
     assert tmpdir.strpath not in sys.path
 
 
+def test_python_rc(shell, tmpdir, monkeypatch, capsys, xession, mocker):
+    """Test that python based control files are executed using Python's parser"""
+
+    monkeypatch.setattr(sys.stdin, "isatty", lambda: True)
+    monkeypatch.setitem(os.environ, "XONSH_CACHE_SCRIPTS", "False")
+
+    # spy on xonsh's compile method
+    spy = mocker.spy(xession.execer, "compile")
+
+    rc = tmpdir.join("rc.py")
+    rc.write("print('Hello World!')")
+    xonsh.main.premain(["--rc", rc.strpath])
+
+    assert rc.strpath in xession.rc_files
+
+    stdout, stderr = capsys.readouterr()
+    assert "Hello World!" in stdout
+    assert len(stderr) == 0
+
+    # Check that the temporary rc's folder is not left behind on the path
+    assert tmpdir.strpath not in sys.path
+    assert spy.called == False
+
+
 def test_rcdir(shell, tmpdir, monkeypatch, capsys):
     """
     Test that files are loaded from an rcdir, after a normal rc file,

xonsh/codecache.py

@@ -105,6 +105,10 @@ def compile_code(filename, code, execer, glb, loc, mode):
     """
     Wrapper for ``execer.compile`` to compile the given code
     """
+
+    if filename.endswith(".py") and mode == "exec":
+        return compile(code, filename, mode)
+
     if not code.endswith("\n"):
         code += "\n"
     old_filename = execer.filename