6 ms·

Its not all roses; I tried to comment out a few routes in my clojure compojure code by doing something like this to my code a while back. (defroutes data-rou

Its not all roses; I tried to comment out a few routes in my clojure compojure code by doing something like this to my code a while back. (defroutes data-routes (GET "/something1" [] (sample-json-data)) (GET "/something2" [] "hello1") (comment (GET "/something3" [] "hello3") (GET "/something4" [] "hello4")) GET "/something5" [] "hello5") ) Then when a client tried to access /something5 , I began getting null pointer execptions. This took me a while to figure out what I had done wrong.

Borkdude 6y ago
In that case you should use a reader ignore: #_(GET "/something3" [] "hello3")
- nimih 6y ago
  The reader ignore macro can be stacked in clojure, so you can also do #_#_#_#_GET "/something3" [] "hello3" if it strikes your fancy. The possibilities for bikeshedding here are truly remarkable.
clojurenoob 6y ago
I notice I accidently do similiar thing with parenedit. I can accidently move forms in and out of where they should be. Not an issue if the functions are small but with longer ones I might slurp off screen.
bjoli 6y ago
Common mistake. For non-lispers: Macros evaluate from the outside, which means the defroutes macro will expand before the (comment ...) macro. For this to reliably work, you need a reader macro that removes the code before macro expansion. I don't know if clojure has that, but common lisp and some schemes have utilities for it.
nimih 6y ago
The comment macro should really come with a warning that it should only be used as a top level form. Using it inline (a very natural thing to do if you're coming from a language with more typical block comments!) only ever leads to suffering, in my experience.
hombre_fatal 6y ago
I notice default syntax highlighting in Emacs, Vim, and VSCode make that odd-one-out "GET" a different color than the rest which would make this a lot easier to catch than otherwise.

Borkdude 6y ago

In that case you should use a reader ignore: #_(GET "/something3" [] "hello3")

nimih 6y ago
The reader ignore macro can be stacked in clojure, so you can also do #_#_#_#_GET "/something3" [] "hello3" if it strikes your fancy. The possibilities for bikeshedding here are truly remarkable.

clojurenoob 6y ago

I notice I accidently do similiar thing with parenedit. I can accidently move forms in and out of where they should be. Not an issue if the functions are small but with longer ones I might slurp off screen.

bjoli 6y ago

Common mistake. For non-lispers: Macros evaluate from the outside, which means the defroutes macro will expand before the (comment ...) macro. For this to reliably work, you need a reader macro that removes the code before macro expansion. I don't know if clojure has that, but common lisp and some schemes have utilities for it.

nimih 6y ago

The comment macro should really come with a warning that it should only be used as a top level form. Using it inline (a very natural thing to do if you're coming from a language with more typical block comments!) only ever leads to suffering, in my experience.

hombre_fatal 6y ago

I notice default syntax highlighting in Emacs, Vim, and VSCode make that odd-one-out "GET" a different color than the rest which would make this a lot easier to catch than otherwise.