Express routing: how to return 404 error on static file and maintain HTML5Mode for angular ui-router

Question

I have a AngularJS webpage using ui-router for routing on HTML5Mode, that it means that URL doesn't have to have "index.html#" neither '#'.

To achieve that I configured my express as ui-router wiki says:

app.use('/app',         express.static(__dirname + '/../web/app'));
app.use('/css',         express.static(__dirname + '/../web/css'));
app.use('/img',         express.static(__dirname + '/../web/img'));
app.use('/libs',        express.static(__dirname + '/../web/libs'));
app.use('/views',       express.static(__dirname + '/../web/views'));
app.all('/*', function(req, res, next) {
    res.sendFile(path.resolve(__dirname + '/../web/index.html'));
});

The important part is last line, all calls that doesn't match app/css/img... return index.html

It works, the problem comes because I have another rule to return public files:

// Return file
app.use('/file',        express.static(__dirname + "/../public/", options));

In the angular app I use $http to get a public file (file name is a parameter on URL) and if file exists I do something with it:

var fileUrl = "http://mydomain/file/" + $stateParams.filename + '.png';
$http.get(fileUrl)
    .then(
        function(response){
            if(response.status == 200){
                // File exist
            }
        }
    );

The problem is that even if file doesn't exist I always get a response with an status of 200. Express routing tried to return the file but as it doesn't exist it return index.html. That is what I think happens

Recap:

http://mydomain/file/fileThatExist.png Returs Image http://mydomain/file/fileThatDoesNotExit.png Returs index.html

I tried to use a regex but it had same effect

// All calls that doesn't contain 'file' string

/*
    ^      # Start of string
    (?!    # Assert that it's impossible to match...
     file  # file, followed by
     $     # end of string
    )      # End of negative lookahead assertion
    .*     # Now match anything
*/

app.all(/^\/(?!file$).*/, function(req, res, next) {
    res.sendFile(path.resolve(__dirname + '/../web/index.html'));
});

Any help is welcome.