Re: with-redefs does not work for macros

[Tiago Espinha]

It's definitely good to mention. It's also what I ended up doing but didn't 
mention it in my answer :)



On Tue, Nov 1, 2016 at 1:15 AM +0100, "Beau Fabry" 
> wrote:

Not an answer to your question, but I usually just redefine 
clojure.tools.logging/log* instead for tests.

On Monday, April 27, 2015 at 9:34:14 AM UTC-7, Vebjorn Ljosa wrote:
In one of my tests, I was trying to mock something 
(`clojure.tools.logging/warn`) that happened to be a macro. It had me puzzled 
for a while until I discovered that `with-redefs` resets the value of the vars 
after the body is executed, but does not reset the flag that says that the var 
is a macro:

$ lein repl
Clojure 1.6.0
...
user=> (defmacro foo [] `(prn "I am a macro"))
#'user/foo
user=> (clojure.test/function? 'foo)
false
user=> (with-redefs [foo (fn [] 42)])
nil
user=> (clojure.test/function? foo)
true
user=> (foo)
ArityException Wrong number of args (0) passed to: user/foo 
clojure.lang.AFn.throwArity (AFn.java:429)
user=> (foo 42 42)
(clojure.core/prn "I am a macro")

Is this a bug?

I looked at the source for `with-redefs-fn`, and the fix appears simple: record 
for each val whether it's a macro or not, and then call the `(setMacro)` method 
on the vars that should be macros after resetting their values.

Vebjorn

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Re: with-redefs does not work for macros

[Tiago Espinha]

Damn it, I got exactly the same thing. In my case when trying to mock the 
/error fun...ehem...macro :-)

There should definitely be some kind of warning or even an error. It 
doesn't make sense to mock macros since these are expanded at compile time.

On Monday, April 27, 2015 at 8:03:43 PM UTC+2, Vebjorn Ljosa wrote:

> On Monday, April 27, 2015 at 12:34:14 PM UTC-4, Vebjorn Ljosa wrote:
>>
>> In one of my tests, I was trying to mock something 
>> (`clojure.tools.logging/warn`) that happened to be a macro. It had me 
>> puzzled for a while until I discovered that `with-redefs` resets the value 
>> of the vars after the body is executed, but does not reset the flag that 
>> says that the var is a macro:
>>
>
> Granted, using `with-redefs` with a macro rarely makes sense because 
> macroexpansion has to occur within the extent of `with-redefs` for the 
> redefinition to have any effect. (I can't even think of an example where I 
> would want to do that, so maybe `with-redefs` should emit a warning when 
> it's being asked to redefine a macro.) But in any case, an attempt to use 
> `with-redefs` on something that happens to be a macro should not mess up 
> the root binding permanently.
>

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