Editing Combine quickfix steps

Various packages are available to check source code for style compliance or to identify errors such as using a variable before a value is assigned to it. For Python code, two such packages are [http://pypi.python.org/pypi/pyflakes pyflakes] and [http://pypi.python.org/pypi/pep8 pep8]. It is convenient to configure Vim's <code>:make</code> command to invoke one of the programs and display any errors in the quickfix window. This tip shows how to run <code>:make</code> multiple times and combine the errors into one quickfix list.

After sourcing the following code, edit a Python file and type <code>:Pycheck</code> to check the code with both <code>pyflakes</code> and <code>pep8</code> (each of these needs to be installed).

The script defines a user command (<code>Pycheck</code>) that invokes the <code>DoMake</code> function, specifying the names of the programs to be run to check the current file. Any changes to the file are saved. Each program name provided (there can be any number) is used to set the <code>'makeprg'</code> option, then <code>:make!</code> is run to invoke the program and set the quickfix list from the results. The <code>!</code> option avoids jumping to the first error, if any (later, the script jumps to the first error for the first program, if applicable), while <code>silent</code> prevents the display of normal messages that result from running <code>:make</code> in order to avoid the "Press Enter" prompt.

The quickfix list from each run of <code>:make</code> is appended to <code>qflist</code> (a variable initialised to <code>[]</code> or an empty list). When finished, <code>qflist</code> holds all quickfix messages resulting from running each of the programs. If the list is empty, the quickfix window is closed (if it was currently open from a previous run). Otherwise, the list is used to set Vim's quickfix list, and the quickfix window is opened and the first error displayed.