Re: Understanding remove-ns and require

[Mikhail Gusarov]

On Fri, 22 Dec 2017, at 18:41, Stuart Sierra wrote:
> Also be aware that AOT-compilation[1] causes all sorts of havoc with
> namespace reloading, because AOT-compiled .class files get read by a
> different ClassLoader.> 

Is there any place explaining how exactly Clojure compiles and loads the
code? It always feels like magic (especially when it does not work).
Names of source code files work too.

Links:

  1. https://clojure.org/reference/compilation

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Re: Understanding remove-ns and require

[Andy Fingerhut]

If you do have namespace names that do not correspond with the file name
they are placed in, in a Clojure/Java files, Eastwood can find them for you
quickly.  Eastwood doesn't analyze ClojureScript files, though.

Andy

https://github.com/jonase/eastwood


On Fri, Dec 22, 2017 at 9:41 AM, Stuart Sierra 
wrote:

> => CompilerException java.lang.Exception: namespace 'foo.bar' not found
>> after loading '/foo/bar', compiling:(*cider-repl foo*:65:7)
>>
>
> An error like this usually means that the ns declaration does not match
> the expected namespace name, based on the file path.
>
> Also be aware that AOT-compilation
>  causes all sorts of havoc
> with namespace reloading, because AOT-compiled .class files get read by a
> different ClassLoader. In effect, you cannot "unload" an AOT-compiled
> namespace. Make sure you do not have any AOT-compiled .class files in your
> project, and note that some tools and templates enable AOT by default.
>
> –S
>
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Re: Understanding remove-ns and require

[Stuart Sierra]

>
> => CompilerException java.lang.Exception: namespace 'foo.bar' not found 
> after loading '/foo/bar', compiling:(*cider-repl foo*:65:7)
>

An error like this usually means that the ns declaration does not match the 
expected namespace name, based on the file path.

Also be aware that AOT-compilation 
 causes all sorts of havoc with 
namespace reloading, because AOT-compiled .class files get read by a 
different ClassLoader. In effect, you cannot "unload" an AOT-compiled 
namespace. Make sure you do not have any AOT-compiled .class files in your 
project, and note that some tools and templates enable AOT by default.

–S

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Re: Understanding remove-ns and require

[Mark Melling]

Thanks Andy, that was helpful.

In my example foo.bar is in *loaded-libs*

I removed it by calling (clojure.tools.namespace.reload/remove-lib 'foo.bar)

Interestingly when I then did a require I get a different error, the file
is loaded, but the namespace not found.

(require '[foo.bar :as bar])
=> CompilerException java.lang.Exception: namespace 'foo.bar' not found
after loading '/foo/bar', compiling:(*cider-repl foo*:65:7)

Cheers

Mark



On Wed, 20 Dec 2017 at 00:30 Andy Fingerhut 
wrote:

> I don't have the answer, but perhaps a clue that might lead you to one:
> the function remove-lib inside of the tools.namespace library does this:
>
> (defn remove-lib
>   "Remove lib's namespace and remove lib from the set of loaded libs."
>   [lib]
>   (remove-ns lib)
>   (dosync (alter @#'clojure.core/*loaded-libs* disj lib)))
>
> I suspect that perhaps since in your example REPL session you are not
> doing anything to change clojure.core/*loaded-libs*, that perhaps it still
> contains the namespace name on which you called remove-ns.  *loaded-libs*
> is modified by functions used to implement the behavior of 'require',
> because require tries to avoid re-loading namespaces that have already been
> loaded earlier.
>
> Andy
>
> On Tue, Dec 19, 2017 at 2:14 PM, Mark Melling <
> mark.mell...@savageminds.com> wrote:
>
>> Hi,
>>
>> Apologies in advance for the possibly stupid question!
>>
>> I was having a problem with clojure.tools.namespace.repl/refresh where a
>> namespace that had been successfully loaded subsequently failed to be
>> reloaded when doing a repl/refresh.
>>
>> Whilst investigating the problem, (this is probably totally unrelated to
>> my issue), I realised I didn't understand how remove-ns and require
>> actually work.
>>
>> To illustrate this I did the following:
>>
>> (require '[foo.bar :as bar])
>> => nil
>> (remove-ns 'foo.bar)
>> => #namespace[foo.bar]
>> (require '[foo.bar :as bar])
>> => CompilerException java.lang.Exception: namespace 'foo.bar' not found,
>> compiling:(*cider-repl foo*:30:7)
>>
>>
>>
>>
>> So what does remove-ns do to cause the second require to fail?
>>
>>
>>
>> Thanks
>>
>> Mark
>>
>>
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Re: Understanding remove-ns and require

[Andy Fingerhut]

I don't have the answer, but perhaps a clue that might lead you to one: the
function remove-lib inside of the tools.namespace library does this:

(defn remove-lib
  "Remove lib's namespace and remove lib from the set of loaded libs."
  [lib]
  (remove-ns lib)
  (dosync (alter @#'clojure.core/*loaded-libs* disj lib)))

I suspect that perhaps since in your example REPL session you are not doing
anything to change clojure.core/*loaded-libs*, that perhaps it still
contains the namespace name on which you called remove-ns.  *loaded-libs*
is modified by functions used to implement the behavior of 'require',
because require tries to avoid re-loading namespaces that have already been
loaded earlier.

Andy

On Tue, Dec 19, 2017 at 2:14 PM, Mark Melling 
wrote:

> Hi,
>
> Apologies in advance for the possibly stupid question!
>
> I was having a problem with clojure.tools.namespace.repl/refresh where a
> namespace that had been successfully loaded subsequently failed to be
> reloaded when doing a repl/refresh.
>
> Whilst investigating the problem, (this is probably totally unrelated to
> my issue), I realised I didn't understand how remove-ns and require
> actually work.
>
> To illustrate this I did the following:
>
> (require '[foo.bar :as bar])
> => nil
> (remove-ns 'foo.bar)
> => #namespace[foo.bar]
> (require '[foo.bar :as bar])
> => CompilerException java.lang.Exception: namespace 'foo.bar' not found,
> compiling:(*cider-repl foo*:30:7)
>
>
>
>
> So what does remove-ns do to cause the second require to fail?
>
>
>
> Thanks
>
> Mark
>
>
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Understanding remove-ns and require

[Mark Melling]

Hi,

Apologies in advance for the possibly stupid question!

I was having a problem with clojure.tools.namespace.repl/refresh where a 
namespace that had been successfully loaded subsequently failed to be 
reloaded when doing a repl/refresh.

Whilst investigating the problem, (this is probably totally unrelated to my 
issue), I realised I didn't understand how remove-ns and require actually 
work. 

To illustrate this I did the following:

(require '[foo.bar :as bar])
=> nil
(remove-ns 'foo.bar)
=> #namespace[foo.bar]
(require '[foo.bar :as bar])
=> CompilerException java.lang.Exception: namespace 'foo.bar' not found, 
compiling:(*cider-repl foo*:30:7)




So what does remove-ns do to cause the second require to fail? 



Thanks

Mark
 

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