if optional term in the route, params are shifted in req.params (ROR)

[doom-fr]

I am using express (4.10.6) with a route that has a optional term.

app.get("/truc(muche)?/bidule/:machin/:chose",my_function);

The route work great as /truc/bidule/head/foot and /trucmuche/bidule/head/foot is well routed to my_function.

But there's a problem because when entering the function,the req.params is :

for /truc :      { '0': 'foot', machin: undefined, chose: 'head' }
for /trucmuche : { '0': 'foot', machin: 'muche', chose: 'head' }

instead of what seems to be expected :

for /truc :      { '0': undefined, machin: 'head', chose: 'foot' }
for /trucmuche : { '0': 'muche', machin: 'head', chose: 'foot' }

Strange !

Thanks for your help.

Doom.

[dougwilson]

It's unfortunate it's a bug in the old version of path-to-regexp we use, and since it's so old, it may not get fixed. In the meantime, you can always use the path /:first(truc(muche)?)/bidule/:machin/:chose (i.e. give the first path segment a name and the regexp to metch for it).

[dougwilson]

Basically the limitation of the path-to-regexp we are using is that you cannot have your own capture groups before named parameters in the path.

[dougwilson]

Good news! This is now fixed in path-to-regexp 0.1.5, which is Express 4.x compatible! Bad news is we cannot yet moved to 0.1.5 until the following bug is fixed: pillarjs/path-to-regexp#55