more tests, news and docs

docs/tutorial.rst

@@ -526,6 +526,28 @@ feed them to a subprocess as needed.  For example:
     for i in range(20):
         $[touch @('file%02d' % i)]
 
+The ``@()`` syntax may also be used inside of subprocess
+arguments, not just as a stand-alone argument. For example:
+
+  .. code-block:: xonshcon
+
+    >>> x = 'hello'
+    >>> echo /path/to/@(x)
+    /path/to/hello
+
+When used inside of a subprocess argument and ``<expr>`` evaluates to a
+non-string iterable, ``@()`` will expand to the outer product of all
+given values:
+
+  .. code-block:: sh
+
+    >>> echo /path/to/@(['hello', 'world'])
+    /path/to/hello /path/to/world
+
+    >>> echo @(['a', 'b']):@('x', 'y')
+    a:x a:y b:x b:y
+
+
 Command Substitution with ``@$()``
 ==================================
 

news/atin.rst

@@ -0,0 +1,33 @@
+**Added:**
+
+* The python-mode ``@(expr)`` syntax may now be used inside of subprocess
+  arguments, not just as a stand-alone argument. For example:
+
+  .. code-block:: sh
+
+    $ x = 'hello'
+    $ echo /path/to/@(x)
+    /path/to/hello
+
+  This syntax will even properly expand to the outer product if the ``expr``
+  is a list (or other non-string iterable) of values:
+
+  .. code-block:: sh
+
+    $ echo /path/to/@(['hello', 'world'])
+    /path/to/hello /path/to/world
+
+    $ echo @(['a', 'b']):@('x', 'y')
+    a:x a:y b:x b:y
+
+  Previously this was not possible.
+
+**Changed:** None
+
+**Deprecated:** None
+
+**Removed:** None
+
+**Fixed:** None
+
+**Security:** None

tests/test_builtins.py

@@ -17,6 +17,7 @@ from xonsh.built_ins import (
     superhelper,
     ensure_list_of_strs,
     list_of_strs_or_callables,
+    list_of_list_of_strs_outer_product,
     regexsearch,
     globsearch,
     expand_path,
@@ -142,6 +143,19 @@ def test_list_of_strs_or_callables(exp, inp):
     assert exp == obs
 
 
+@pytest.mark.parametrize(
+    "inp, exp",
+    [
+        (["x", ["y", "z"]], ["xy", "xz"]),
+        (["x", ["y", "z"], ["a"]], ["xya", "xza"]),
+        ([["y", "z"], ["a", "b"]], ["ya", "yb", "za", "zb"]),
+    ],
+)
+def test_list_of_list_of_strs_outer_product(xonsh_builtins, inp, exp):
+    obs = list_of_list_of_strs_outer_product(inp)
+    assert exp == obs
+
+
 @pytest.mark.parametrize(
     "s",
     [

tests/test_parser.py

@@ -2063,6 +2063,7 @@ def test_nested_madness():
 def test_atparens_intoken():
     check_xonsh_ast({}, "![echo /x/@(y)/z]", False)
 
+
 def test_ls_dot_nesting():
     check_xonsh_ast({}, '$(ls @(None or "."))', False)
 

xonsh/built_ins.py

@@ -977,8 +977,8 @@ def list_of_list_of_strs_outer_product(x):
     lolos = map(ensure_list_of_strs, x)
     rtn = []
     for los in itertools.product(*lolos):
-        s = ''.join(los)
-        if '*' in s:
+        s = "".join(los)
+        if "*" in s:
             rtn.extend(builtins.__xonsh_glob__(s))
         else:
             rtn.append(builtins.__xonsh_expand_path__(s))
@@ -1250,7 +1250,9 @@ def load_builtins(execer=None, ctx=None):
     builtins.__xonsh_all_jobs__ = {}
     builtins.__xonsh_ensure_list_of_strs__ = ensure_list_of_strs
     builtins.__xonsh_list_of_strs_or_callables__ = list_of_strs_or_callables
-    builtins.__xonsh_list_of_list_of_strs_outer_product__ = list_of_list_of_strs_outer_product
+    builtins.__xonsh_list_of_list_of_strs_outer_product__ = (
+        list_of_list_of_strs_outer_product
+    )
     builtins.__xonsh_completers__ = xonsh.completers.init.default_completers()
     builtins.__xonsh_call_macro__ = call_macro
     builtins.__xonsh_enter_macro__ = enter_macro

xonsh/parsers/base.py

@@ -3123,7 +3123,9 @@ class BaseParser(object):
             # has an expanding function call, such as @(x)
             p0 = xonsh_call(
                 "__xonsh_list_of_list_of_strs_outer_product__",
-                args=[ensure_has_elts(p1)], lineno=p1[0].lineno, col=p1[0].col_offset
+                args=[ensure_has_elts(p1)],
+                lineno=p1[0].lineno,
+                col=p1[0].col_offset,
             )
             p0._cliarg_action = "extend"
         elif hasglobstar(p1):
@@ -3192,7 +3194,7 @@ class BaseParser(object):
             "DOLLAR_LBRACKET",
             "ATDOLLAR_LPAREN",
         }
-        ts = "\n                 | ".join(sorted([t.lower() + '_tok' for t in toks]))
+        ts = "\n                 | ".join(sorted([t.lower() + "_tok" for t in toks]))
         doc = "subproc_arg_part : " + ts + "\n"
         self.p_subproc_arg_part.__func__.__doc__ = doc