#511: Add ln_s_order rule

README.md

@@ -191,6 +191,7 @@ using the matched rule and runs it. Rules enabled by default are as follows:
 * `javac` – appends missing `.java` when compiling Java files;
 * `lein_not_task` – fixes wrong `lein` tasks like `lein rpl`;
 * `ln_no_hard_link` – catches hard link creation on directories, suggest symbolic link;
+* `ln_s_order` – fixes `ln -s` arguments order;
 * `ls_lah` – adds `-lah` to `ls`;
 * `man` – changes manual section;
 * `man_no_space` – fixes man commands without spaces, for example `mandiff`;

tests/rules/test_ln_no_hard_link.py

@@ -20,7 +20,7 @@ def test_match(script, stderr):
     ("ln a b", "... hard link"),
     ("sudo ln a b", "... hard link"),
     ("a b", error)])
-def test_assert_not_match(script, stderr):
+def test_not_match(script, stderr):
     command = Command(script, stderr=stderr)
     assert not match(command)
 

tests/rules/test_ln_s_order.py

@@ -0,0 +1,41 @@
+import pytest
+from thefuck.rules.ln_s_order import match, get_new_command
+from tests.utils import Command
+
+
+@pytest.fixture
+def file_exists(mocker):
+    return mocker.patch('os.path.exists', return_value=True)
+
+
+get_stderr = "ln: failed to create symbolic link '{}': File exists".format
+
+
+@pytest.mark.usefixtures('file_exists')
+@pytest.mark.parametrize('script', [
+    'ln -s dest source',
+    'ln dest -s source',
+    'ln dest source -s'])
+def test_match(script):
+    stderr = get_stderr('source')
+    assert match(Command(script, stderr=stderr))
+
+
+@pytest.mark.parametrize('script, stderr, exists', [
+    ('ln dest source', get_stderr('source'), True),
+    ('ls -s dest source', get_stderr('source'), True),
+    ('ln -s dest source', '', True),
+    ('ln -s dest source', get_stderr('source'), False)])
+def test_not_match(file_exists, script, stderr, exists):
+    file_exists.return_value = exists
+    assert not match(Command(script, stderr=stderr))
+
+
+@pytest.mark.usefixtures('file_exists')
+@pytest.mark.parametrize('script, result', [
+    ('ln -s dest source', 'ln -s source dest'),
+    ('ln dest -s source', 'ln -s source dest'),
+    ('ln dest source -s', 'ln source -s dest')])
+def test_match(script, result):
+    stderr = get_stderr('source')
+    assert get_new_command(Command(script, stderr=stderr)) == result

thefuck/rules/ln_no_hard_link.py

@@ -15,7 +15,7 @@ from thefuck.specific.sudo import sudo_support
 @sudo_support
 def match(command):
     return (command.stderr.endswith("hard link not allowed for directory") and
-            command.script.startswith("ln "))
+            command.script_parts[0] == 'ln')
 
 
 @sudo_support

thefuck/rules/ln_s_order.py

@@ -0,0 +1,26 @@
+import os
+from thefuck.specific.sudo import sudo_support
+
+
+def _get_destination(script_parts):
+    """When arguments order is wrong first argument will be destination."""
+    for part in script_parts:
+        if part not in {'ln', '-s', '--symbolic'} and os.path.exists(part):
+            return part
+
+
+@sudo_support
+def match(command):
+    return (command.script_parts[0] == 'ln'
+            and {'-s', '--symbolic'}.intersection(command.script_parts)
+            and 'File exists' in command.stderr
+            and _get_destination(command.script_parts))
+
+
+@sudo_support
+def get_new_command(command):
+    destination = _get_destination(command.script_parts)
+    parts = command.script_parts[:]
+    parts.remove(destination)
+    parts.append(destination)
+    return ' '.join(parts)