Merge pull request #77 from matthew-brett/allow-py23-choice

MRG: allow choice of Python version in vimrc

Author: kevinw

README.rst

@@ -89,11 +89,24 @@ Options
 -------
 
 Set this option in your vimrc file to disable quickfix support::
-    
+
     let g:pyflakes_use_quickfix = 0
 
 The value is set to 1 by default.
 
+Pyflakes can use Python 2 or Python 3 compiled into Vim.  If you have both,
+you can ask Pyflakes to prefer one or the other, with this in your vimrc::
+
+    let g:pyflakes_prefer_python_version = 3
+
+or::
+
+    let g:pyflakes_prefer_python_version = 2
+
+Pyflakes will chose Python 2 by default, if you have both.  If you prefer a
+version that you don't have, Pyflakes will quietly fall back to the version
+that you do have.
+
 TODO
 ----
  * signs_ support (show warning and error icons to left of the buffer area)

ftplugin/python/pyflakes.vim

@@ -24,19 +24,32 @@ endif
 if !exists("b:did_python_init")
     let b:did_python_init = 0
 
+    if !has('python') && !has('python3')
+        echoerr "Error: Requires Vim compiled with +python or +python3"
+        finish
+    endif
+    " Default to Python 2
     if has('python')
+        let py_cmd_ver = 'python'
+    else
+        let py_cmd_ver = 'python3'
+    endif
+    if exists('g:pyflakes_prefer_python_version')
+        if g:pyflakes_prefer_python_version == 3 && has('python3')
+            let py_cmd_ver = 'python3'
+        elseif g:pyflakes_prefer_python_version == 2 && has('python')
+            let py_cmd_ver = 'python'
+        endif
+    endif
+    if py_cmd_ver == 'python'
         command! -nargs=1 Python python <args>
-    elseif has('python3')
-        command! -nargs=1 Python python3 <args>
     else
-        echo "Error: Requires Vim compiled with +python or +python3"
-        finish
+        command! -nargs=1 Python python3 <args>
     endif
 
-if !exists('g:pyflakes_use_quickfix')
-    let g:pyflakes_use_quickfix = 1
-endif
-
+    if !exists('g:pyflakes_use_quickfix')
+        let g:pyflakes_use_quickfix = 1
+    endif
 
 Python << EOF
 import vim