MatchEm is a vim plugin which auto adds closing quotes, parens, brackets, curlies and other such characters as you type. Using matchem doesn't involve any change of behavior on your part. Simple type your code as you normally would and matchem will handle auto adding closing quotes, etc as necessary and overwriting them accordingly if you continue to manually type the closing character.
tl;dr Matchem is built to handle edge cases not handled by delimitMate and other similar plugins.
At this point delimitMate seems to be the standard plugin to choose for auto adding of closing characters. DelimitMate is a great plugin and while writing matchem I quickly learned how much effort goes into a seemingly simple plugin so I certainly don't want to diminish its usefulness.
However, after using delimiteMate for awhile I found myself running into several edge cases where delimitMate didn't do the right thing and I had to stop, correct its mistake, then get back to what I was doing. This happened enough that I removed delimitMate altogether, but then I found my self missing it for the cases it did get right. I looked at the delimitMate code in hopes to just updated it to handle the edge cases, but I decided that it might be easier to just start from scratch.
Matchem was written with the intention to clearly address as many edge cases as possible (and provide the means to inject your own edge case handlers) so that you aren't interrupting your flow by correcting mistakes made by the matcher.
Below is a non-comprehensive list of various scenarios where delimitMate didn't do the right thing. The example text you see is the result when using matchem, but you can try typing these "as is" using delimitMate to see how it handles these cases. For the cases with "before:" and "after:", the | denotes where the insert was started on the existing "before" text.
Handle not auto-adding closing curly if one already exists on a lower line
if (foo){ }else{ }Better handling of when closing character should be added or overwritten
before: foo = ("bar", |"baz"|) after: foo = ("bar", ("baz"))Inserting a quoted string before another quoted string
before: (|"foo") after: ("bar", "foo")Inserting quotes inside existing matched characters in a string
before: foo = "bar[|i]" after: foo = "bar[" + i + "]"
Wrapping open/close characters around existing code
before: foo = |(bar) after: foo = [(bar)]
Don't consider an escaped quote as a match when deciding when to overwrite
foo = "\""
Don't auto match < when typing within script tags in html and php files
<html> <script> if (foo < 0){ } </script> </html>Python unicode and raw string matching
u'test' r'test'
Python triple quote string matching.
""" Test """
Don't auto match ' in lisp, scheme, etc files.
Avoid matching quotes on trailing vim script comments.
function Test() " test comment
Better undo/repeat support. Still not perfect due to at least one outstanding vim bug that delimiMate suffers from as well.