Add a fix function for breaking up long Python lines, which is hidden for now

autoload/ale/fixers/generic_python.vim

@@ -23,3 +23,38 @@ function! ale#fixers#generic_python#AddLinesBeforeControlStatements(buffer, line
 
     return l:new_lines
 endfunction
+
+" This function breaks up long lines so that autopep8 or other tools can
+" fix the badly-indented code which is produced as a result.
+function! ale#fixers#generic_python#BreakUpLongLines(buffer, lines) abort
+    " Default to a maximum line length of 79
+    let l:max_line_length = 79
+    let l:conf = ale#path#FindNearestFile(a:buffer, 'setup.cfg')
+
+    " Read the maximum line length from setup.cfg
+    if !empty(l:conf)
+        for l:match in ale#util#GetMatches(
+        \   readfile(l:conf),
+        \   '\v^ *max-line-length *\= *(\d+)',
+        \)
+            let l:max_line_length = str2nr(l:match[1])
+        endfor
+    endif
+
+    let l:new_list = []
+
+    for l:line in a:lines
+        if len(l:line) > l:max_line_length && l:line !~# '# *noqa'
+            let l:line = substitute(l:line, '\v([(,])([^)])', '\1\n\2', 'g')
+            let l:line = substitute(l:line, '\v([^(])([)])', '\1,\n\2', 'g')
+
+            for l:split_line in split(l:line, "\n")
+                call add(l:new_list, l:split_line)
+            endfor
+        else
+            call add(l:new_list, l:line)
+        endif
+    endfor
+
+    return l:new_list
+endfunction

test/fixers/long-line-project/setup.cfg

@@ -0,0 +1,2 @@
+[flake8]
+max-line-length = 90

test/fixers/test_break_up_long_lines_python_fixer.vader

@@ -0,0 +1,39 @@
+Before:
+  call ale#test#SetDirectory('/testplugin/test/fixers')
+
+After:
+  call ale#test#RestoreDirectory()
+
+Execute(Long lines with basic function calls should be broken up correctly):
+  AssertEqual
+  \ [
+  \   'def foo():',
+  \   '    some_variable = this_is_a_longer_function(',
+  \   'first_argument,',
+  \   ' second_argument,',
+  \   ' third_with_function_call(',
+  \   'foo,',
+  \   ' bar,',
+  \   '))',
+  \ ],
+  \ ale#fixers#generic_python#BreakUpLongLines(bufnr(''), [
+  \   'def foo():',
+  \   '    some_variable = this_is_a_longer_function(first_argument, second_argument, third_with_function_call(foo, bar))',
+  \ ])
+
+Execute(Longer lines should be permitted if a configuration file allows it):
+  call ale#test#SetFilename('long-line-project/foo/bar.py')
+
+  AssertEqual
+  \ [
+  \   'x = this_line_is_between_79_and_90_characters(first, second, third, fourth, fifth)',
+  \   'y = this_line_is_longer_than_90_characters(',
+  \   'much_longer_word,',
+  \   ' another_longer_word,',
+  \   ' a_third_long_word,',
+  \   ')'
+  \ ],
+  \ ale#fixers#generic_python#BreakUpLongLines(bufnr(''), [
+  \   'x = this_line_is_between_79_and_90_characters(first, second, third, fourth, fifth)',
+  \   'y = this_line_is_longer_than_90_characters(much_longer_word, another_longer_word, a_third_long_word)',
+  \ ])