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[NREPL-28] Clarify semantics for String encoding Created: 21/Aug/12  Updated: 11/Oct/12

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Critical
Reporter: Chas Emerick Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Comments   
Comment by Chas Emerick [ 21/Aug/12 8:27 PM ]

Initial discussion held in NREPL-11.





[NREPL-53] Middleware linearization is nondeterministically wrong Created: 02/May/14  Updated: 19/Aug/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.3
Fix Version/s: None

Type: Defect Priority: Critical
Reporter: Gary Fredericks Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None
Environment:

clojure 1.6.0



 Description   

I've had trouble getting my middleware ordered correctly, and have wittled it down to the following example which seems to only fail in some processes. I.e., it is deterministic within a particular jvm, but across jvms the result can change. My guess is that this has to do with hashing vars.

This code prints true (signifying a correct result) roughly 1/3 of the time and false otherwise.

(ns chas.core
  (:require [clojure.tools.nrepl.middleware :as mid]
            [clojure.tools.nrepl.middleware.pr-values]
            [clojure.tools.nrepl.middleware.session]))

(def wrap-foo identity)
(mid/set-descriptor! #'wrap-foo
                     {:expects #{#'clojure.tools.nrepl.middleware.session/session "eval"}})

(def wrap-bar identity)
(mid/set-descriptor! #'wrap-bar
                     {:requires #{#'clojure.tools.nrepl.middleware.session/session},
                      :expects #{"describe" #'clojure.tools.nrepl.middleware.pr-values/pr-values},
                      :handles {"stacktrace" {}}})

(defn -main
  []
  (println
   ;; should return true, since #'wrap-foo belongs later in the stack than
   ;; #'clojure.tools.nrepl.middleware.session/session due to its :expects
   ;; clause
   (->> [#'wrap-foo
         #'wrap-bar
         #'clojure.tools.nrepl.middleware.session/session]
        (mid/linearize-middleware-stack)
        (filter #{#'clojure.tools.nrepl.middleware.session/session #'wrap-foo})
        (= [#'clojure.tools.nrepl.middleware.session/session #'wrap-foo]))))


 Comments   
Comment by Gary Fredericks [ 02/May/14 10:35 PM ]

Interesting followup observation I made with Alan Malloy in IRC: if we remove "eval" from the :expects clause, it seems to return consistently true. On the other hand if we instead add #'clojure.tools.nrepl.middleware.interruptible-eval/interruptible-eval to the middleware list, suddenly it returns consistently false.

Comment by Gary Trakhman [ 04/Jun/14 3:35 PM ]

I should add my own experience report with this, hope to dig in to it someday soon: https://groups.google.com/d/msg/clojure/nUBBbYZHuTE/ScLBH-A2HkoJ

In my case, it was incorrectness, not indeterminism.

Comment by Chas Emerick [ 19/Aug/14 1:59 PM ]

Half of the middleware linearization stuff is too clever, the other half is really dumb. :-/

I'd love a patch for this. Absent one, I'll have to dig into it, but I'm not going to hold up 0.2.4 any further for that opportunity to come around.

Comment by Gary Fredericks [ 19/Aug/14 2:12 PM ]

Is this a fair summary of the requirements?

1) Should be deterministic
2) Should only return a result that respects the :expects and :requires clauses – if this is impossible it should throw an exception explaining why

Comment by Chas Emerick [ 19/Aug/14 2:58 PM ]

Yes, that's fair. I might add (3) try to not break anything significant that might rely upon undocumented behaviour, but I doubt that's helpful.





[NREPL-24] :session key is overloaded Created: 10/Aug/12  Updated: 03/Oct/12

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Major
Reporter: Hugo Duncan Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

The session middleware takes the :session key from the message, and uses it as an id to lookup session data, which it then places on the same key.

Using a separate key for the session id and the session data would be less confusing, and would allow easier checking of the availability of the session data in the message map.



 Comments   
Comment by Chas Emerick [ 10/Aug/12 11:26 PM ]

The session id will need to continue to come in in the :session slot, as I don't want to break clients (and, there's very, very few middlewares out there yet).

Suggestions for names for the actual session atom? :the-session? :-/





[NREPL-15] Allow clients to specify an ID for newly-retained sessions Created: 29/Mar/12  Updated: 12/Oct/12

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Enhancement Priority: Major
Reporter: Chas Emerick Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

...particularly important where less sophisticated clients and polling-oriented transports are involved (e.g. HTTP).






[NREPL-33] Consider making session and eval functionality more accessible Created: 08/Oct/12  Updated: 18/Nov/12

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.0-beta9
Fix Version/s: None

Type: Defect Priority: Major
Reporter: Hugo Duncan Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

ritz re-uses some of nrepl's private functions to avoid duplication. The uses are listed below.

Would it be possible to make these functions public? More subjectively, it might also be worth considering factoring out the session functionality into it's own namespace (including msg and possibly queue-eval), so the functionality is not split across the session middleware and the interruptible-eval middleware.

The debug nrepl server:
https://github.com/pallet/ritz/blob/develop/nrepl/src/ritz/nrepl.clj#L189

This uses clojure.tools.nrepl.middleware.session/create-session and clojure.tools.nrepl.middleware.session/session-out

ritz provides an eval op that tracks source forms:
https://github.com/pallet/ritz/blob/develop/nrepl-middleware/src/ritz/nrepl/middleware/tracking_eval.clj

This uses clojure.tools.nrepl.middleware.interruptible-eval/queue-eval and clojure.tools.nrepl.middleware.interruptible-eval/configure-executor






[NREPL-4] Provide sane multiplexing of output in the face of multithreaded, asynchronous operation Created: 30/Sep/11  Updated: 03/Oct/12

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Enhancement Priority: Major
Reporter: Chas Emerick Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

Basically, (send-off some-agent println) & co. should get what's printed to out in that agent's thread back to the nREPL client — not silently let it dump out to System/out.

Portal ostensibly does this well. Examine their approach, see if it is compatible with nREPL's objectives.

Ill-formed brain dump:

  • multiplex new out's to System/out
    • (still won't solve clojure.test/test-out content will disappearing into the ether when it's loaded when out is bound to an nREPL out; maybe we should ensure out is bound to System/out while code is being loaded?)
  • optionally multiplex System/out and System/err
  • optionally join multiplexed S/out and S/err, receive :stdout, :stderr msgs





[NREPL-29] Provide a mechanism for overriding an operation Created: 09/Sep/12  Updated: 18/Apr/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.0-beta9, 0.2.0-beta10
Fix Version/s: None

Type: Enhancement Priority: Major
Reporter: Hugo Duncan Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

When specifying middleware, it would be much easier for the user to be able to override a default middleware without having to specify a handler.

For example, if there is a default middleware providing the "complete" operation, the user should be able to just specify their preferred completion middleware, without having to specify all middleware as a handler.

One way to do this might be to check metadata for the provided operations of the specified metadata, and ensure that either the default middleware for that operation is removed, or that the specified middleware takes precendence (which may be simpler when a middleware provides multiple operations).



 Comments   
Comment by Chas Emerick [ 14/Sep/12 7:44 AM ]

Agreed.

Just making sure that the order in which additional middlewares are provided is taken as a default stack order will suffice for most use cases. Transforming middlewares (either in full or in part) would need another metadata slot, :replace perhaps, though it seems like that would be much more difficult to get right.





[NREPL-3] Adopt default port Created: 30/Sep/11  Updated: 13/Jun/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Major
Reporter: Chas Emerick Assignee: Chas Emerick
Resolution: Unresolved Votes: 1
Labels: None


 Description   

7888 is "free", at least in IANA.

Most users want to put an nREPL port on their app, and that should always be on a typical port. Auto-selection of a port is only desirable in tooling scenarios, and tooling authors can pass an argument to start-server.

This will change the behaviour of (start-server).



 Comments   
Comment by Bozhidar Batsov [ 13/Jun/14 9:55 AM ]

Sounds like a good idea.





[NREPL-59] Tracking source form positions in eval Created: 19/Jun/14  Updated: 22/Aug/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.3
Fix Version/s: None

Type: Enhancement Priority: Major
Reporter: Bozhidar Batsov Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: enhancement


 Description   

Dev tools writers using nREPL's eval op face the following problem - using the `eval` op you cannot pass information regarding the filename and the file position of the form you're evaluating and therefore afterwards you can't use find its definition. Because of this most CIDER users reload their source buffers all the time with `load-file`. Another implication of this problem is that exception backtraces have meaningless information about the position of the problem (usually something like `NO_FILE:1`). I've noticed that LightTable has a custom middleware for this, ritz used to have one as well, probably others too. Now I'm contemplating doing something similar for CIDER, but it seems to me this is basic functionality that should be supported out-of-the-box.

I'd like to propose that the default eval middleware be augmented to support some form of source form tracking to spare tool writers from having to reinvent the wheel.



 Comments   
Comment by Chas Emerick [ 19/Aug/14 1:50 PM ]

I agree that this should be baked in. `:line` and `:column` are some optional slots eval could accept (but should not require), with the obvious effect on the reader passed along to the compiler. This may be trickier than it sounds, especially if you're aiming to keep things at parity for both Clojure and ClojureScript (as code to be eval'd is read well before it hits interruptible_eval, in piggieback).

In any case, patch quite welcome.

Comment by Bozhidar Batsov [ 22/Aug/14 2:57 PM ]

`:filepath` should be another optional slot. I don't do much ClojureScript (and I don't know much about piggieback) so getting something working for Clojure would be a good enough start for me. I'll try to cook some patch soon.





[NREPL-43] Document the availability/usage of *e, *1, *2, ... in nREPL Created: 04/Jul/13  Updated: 24/Aug/13

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Enhancement Priority: Minor
Reporter: Jakub Holy Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: documentation


 Description   

I have only by chance discovered that nREPL binds the lat error/outputs to the vars *e, *1 etc. This should be documented clearly somewhere, possibly in https://github.com/clojure/tools.nrepl/blob/master/README.md

When I have forgotten the names of the vars while remembering that something like them exists, I tried to google them out but failed. So better documentation would help.

Thank you!



 Comments   
Comment by Chas Emerick [ 04/Jul/13 7:07 AM ]

The role of those vars is actually the same across all Clojure REPLs. In this department, nREPL is simply following Clojure's lead.

That said, yes, there is room to specify fully what nREPL's behaviour is, beyond the implied equivalence (at a minimum) to Clojure's included console REPL.

Comment by Jakub Holy [ 22/Jul/13 7:37 AM ]

Thank you for the clarification!

> The role of those vars is actually the same across all Clojure REPLs.

Do you know if this behavior of all Clojure REPLs is documented anywhere? And yes, it would be nice if the nREPL documentation linked to this doc and/or it printed a short summary and/or link when starting (in addition to the currently provided info about (source) etc.)

Thanks!

Comment by Chas Emerick [ 22/Jul/13 7:52 AM ]

REPL-bound vars are documented in a variety of places, though nowhere "official" AFAIK. We talked about it in Chapter 10 of Clojure Programming FWIW (I'm certain other books and online resources cover these vars as well, but the CP citation is the only one I have close at hand.)

FYI, the "currently-provided info" you mention is emitted by Leiningen/Reply, not nREPL.

Comment by Jakub Holy [ 24/Aug/13 4:50 AM ]

Thanks a lot, Chas, that was helpful. I have submitted a patch to Leiningen to include the info it its REPL' welcome message: https://github.com/technomancy/leiningen/pull/1310

Comment by Jakub Holy [ 24/Aug/13 5:38 AM ]

I have published a blog post about this, Clojure REPL stores the latest results in *1, *2, *3, exception in *e, to make it more googlable (is that even a word? ).

The top hit for "Clojure REPL" seems to be http://clojure.org/repl_and_main, so it perhaps should be documented there or it should link to a more detailed documentation. Not sure how to make that happen I have also checked http://clojure-doc.org/ but there doesn't seem to be a suitable place to add this info either. Perhaps it should be mentioned in the docstring of clojure.main/repl and the Clojure page should link to it?

Comment by Jakub Holy [ 24/Aug/13 5:52 AM ]

I have created an issue under Clojure itself, #CLJ-1247, so this can likely be closed.





[NREPL-48] *1/*2/*3/*e nil in cloned session Created: 02/Jan/14  Updated: 02/Jan/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Tim Pope Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

Summary says it all. This isn't blocking me; just something I stumbled onto.






[NREPL-36] Too many DynamicClassLoaders created Created: 10/Dec/12  Updated: 18/Apr/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.0-RC1, 0.2.0-beta9, 0.2.0-beta10
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Colin Jones Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

Not sure whether this ticket belongs here or in the Clojure-proper JIRA, so feel free to close if this is an inappropriate location. clojure.main/repl creates a new DynamicClassLoader on every execution, so it looks like the stack of classloaders grows without bounds. Seems a bit similar to http://dev.clojure.org/jira/browse/NREPL-31 in that clojure.main/repl has another assumption about when clojure.main/repl will run.

See https://groups.google.com/forum/?fromgroups=#!topic/clojure/firG9zTVecU%5B1-25%5D for the original report.



 Comments   
Comment by Chas Emerick [ 18/Apr/14 10:17 AM ]

Yes, this should be fixed upstream; a new DynamicClassLoader should only be set as the thread-context classloader if one is not already in place.

My first impulse upon seeing this was that this was "last straw" territory w.r.t. using clojure.main/repl (as recorded in the thread linked above), but the work necessary to stop depending upon it would be considerable (not because repl does much, but because interruptible-eval/evaluate is structured to cater to it). Some years on, and it's clear that this fundamentally a minor problem (insofar as hardly anyone has complained AFAIK), so a fix that requires e.g. Clojure 1.7.0 would be fine.





[NREPL-54] No version of nrepl when connect to the lein-droid REPL Created: 04/May/14  Updated: 31/May/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.3
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Eugene Apollonsky Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None
Environment:

tools.nrepl/0.2.3
lein-droid/0.2.3



 Description   

1. Connect Android device.
2. Start REPL.
lein droid run.
3. Forward port.
lein do droid forward-port, droid repl.
4. Send command {'op': 'describe', 'verbose?': 1}

Result:
...
'versions': { 'clojure': { 'incremental': 0, 'major': 1, 'minor': 6, 'qualifier': 'RC1'},
'nrepl': { }}}



 Comments   
Comment by Chas Emerick [ 05/May/14 11:51 AM ]

The current nREPL version is driven by reading the resource at /clojure/tools/nrepl/version.txt. If it's not found (perhaps because of an android packaging / classloader detail I'm not familiar with?), then no nREPL version will be returned.

FWIW, the version indicator is meant to be strictly advisory, and not really depended upon for e.g. exposing tooling capabilities. What are you needing the version indicator for?

Comment by Eugene Apollonsky [ 05/May/14 1:34 PM ]

Vim plugin "vim-fireplace" has nREPL version check (>0.2.0). OK, I think it can be fixed in the plugin.

Comment by Chas Emerick [ 05/May/14 3:29 PM ]

Yeah, that's likely there to guard against nREPL "classic" (which met its demise ~ 0.0.5). But, that's many years old at this point.

A more interesting question is: why isn't the version file being found by nREPL at load-time? I presume it's an Android-specific idiosyncrasy, but I'm curious nonetheless.

Comment by Eugene Apollonsky [ 31/May/14 4:39 PM ]

lein-droid developer commented this issue. It is Android-specific.
https://github.com/clojure-android/lein-droid/issues/92





[NREPL-55] Support custom value rendering middleware Created: 13/May/14  Updated: 13/May/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.3
Fix Version/s: None

Type: Enhancement Priority: Minor
Reporter: Gregory Look Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

Currently, nREPL's interruptible-eval middleware hardcodes a dependency on pr-values. It would be nicer if the user could either specify alternate rendering middleware or if nREPL's built-in middleware accepted an arbitrary function to render values with. Specifically, this would enable pretty-printing REPL output.

I've set up a middleware to demonstrate this, in combination with the Puget printing library:
https://github.com/greglook/whidbey

Currently it is possible to replace the default middleware, but it involves some ugly runtime metadata manipulation which reaches into the nREPL internals. Addressing this would be another step towards simplifying pretty-printing/color integration in the REPL.






[NREPL-46] nREPL crashes when required more than one time with :reload-all Created: 21/Dec/13  Updated: 25/Aug/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.2
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Alex Fowler Assignee: Chas Emerick
Resolution: Unresolved Votes: 1
Labels: bug
Environment:

Irrelevant, but the provided test case project is for CounterClockWise on Eclipse. Although it should run just fine with vanilla lein.


Attachments: Zip Archive nrepl-test.zip    

 Description   

When the namespace "clojure.tools.nrepl.server" is required more than once with :reload-all option, nREPL crashes. Accrding to current info it occures because some protocol instances get re-evaluated and are no longer the same JVM classes as they were before reload-all.

Steps to reproduce the bug in CCW:
1) Import the project into the workspace
2) Go into the core.clj
3) Click Clojure -> Load file in REPL
4) After the evaluation is complete, try evaluating (+ 1 2) in the repl. You should see no response at all.
5) Try writing something with letters, like "nrepl". The autocompletion will try and freeze and fail with the above exception.
6) Play around more to get a full hang or kill the REPL/Java to revive Eclipse.

Upon trying CCW autocompetion, the following exception occures, what might give some hint as to why:

Exception in thread "nREPL-worker-2" java.lang.IllegalArgumentException: No implementation of method: :send of protocol: #'clojure.tools.nrepl.transport/Transport found for class: clojure.tools.nrepl.middleware.pr_values$pr_values$fn$reify__1283
at clojure.core$_cache_protocol_fn.invoke(core_deftype.clj:541)
at clojure.tools.nrepl.transport$eval7291$fn_7292$G7280_7299.invoke(transport.clj:16)
at clojure.tools.nrepl.middleware.interruptible_eval$evaluate$fn_7726$fn_7739.invoke(interruptible_eval.clj:75)
at clojure.main$repl$fn__6597.invoke(main.clj:279)
at clojure.main$repl.doInvoke(main.clj:277)
at clojure.lang.RestFn.invoke(RestFn.java:1096)
at clojure.tools.nrepl.middleware.interruptible_eval$evaluate$fn__7726.invoke(interruptible_eval.clj:56)
at clojure.lang.AFn.applyToHelper(AFn.java:159)
at clojure.lang.AFn.applyTo(AFn.java:151)
at clojure.core$apply.invoke(core.clj:617)
at clojure.core$with_bindings_STAR_.doInvoke(core.clj:1788)
at clojure.lang.RestFn.invoke(RestFn.java:425)
at clojure.tools.nrepl.middleware.interruptible_eval$evaluate.invoke(interruptible_eval.clj:41)
at clojure.tools.nrepl.middleware.interruptible_eval$interruptible_eval$fn_1345$fn_1348.invoke(interruptible_eval.clj:171)
at clojure.core$comp$fn__4154.invoke(core.clj:2330)
at clojure.tools.nrepl.middleware.interruptible_eval$run_next$fn__7760.invoke(interruptible_eval.clj:138)
at clojure.lang.AFn.run(AFn.java:24)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)



 Comments   
Comment by Chas Emerick [ 19/Aug/14 8:56 PM ]

Confirmed. Using lein repl (though you're right that the particulars of the tooling shouldn't matter):

user=> 3
3
user=> (require '[clojure.tools.nrepl.server] :reload-all)
nil
user=> 2

user=> 1

Not sure if it's the protocol or the types that are implicated (or both), but resolving this is going to be unpleasant.

Comment by Chas Emerick [ 19/Aug/14 8:57 PM ]

Couple of questions:

  • Does the fact that this occurs matter to anyone in a meaningful way?
  • Would an acceptable solution be that reloading of the affected namespaces be no-ops?
Comment by Alex Fowler [ 25/Aug/14 9:34 AM ]

Well, in my case I have a project which is required to often reload various namespaces because they are updated in the background. If it happens that any of the namespaces refer to nrepl, the thing crashes.

The error happens due to implementation problems and is not "a correct error" from the POV of Clojure language so it is better to be fixed. However, of course, in the real world it could be rather hard to do so..

Chas, could you please explain more about the no-ops approach? Do you mean it is possible to somehow force loading nrepl just once?

Comment by Chas Emerick [ 25/Aug/14 10:20 AM ]

Yes, there are ways to prevent the re-definition of types and protocols, but I'd like to avoid doing so. It's a hack, and would be an impediment to developing nREPL itself.

Actually, you should be able to accomplish the same thing more easily in your project: rather than require nREPL namespaces in the ns form, use a top-level require form, wrapped in a suitable conditional to determine if nREPL has been loaded yet:

(when-not (resolve 'clojure.tools.nrepl/version)
  (require 'clojure.tools.nrepl))




[NREPL-64] Add current ns to describe session's response Created: 24/Aug/14  Updated: 27/Aug/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: 0.2.4
Fix Version/s: None

Type: Enhancement Priority: Minor
Reporter: Bozhidar Batsov Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: enhancement


 Description   

In CIDER the REPL buffer gets created on receiving a describe-session response from the nREPL session that will back the REPL buffer. There's a problem with determining the default ns for the REPL buffer as many people use nREPL servers started with lein (lein repl :headless) and expect the `:init-ns` option for their project to the honored, but there's no easy way for clients to know what the default namespace is. It'd be great if this information was returned by `describe-session`.

Perhaps clients should be able to create a session with a particular default namespace to avoid the need for code like https://github.com/technomancy/leiningen/blob/554861505c23763d6583fe3b1f236a08ad02a4ca/src/leiningen/repl.clj#L103. I noticed that current the default ns is hardcoded as `user`.



 Comments   
Comment by Chas Emerick [ 25/Aug/14 8:59 PM ]

As you say, the default nREPL namespace is always user, so that's easy to know.

Leiningen's :init-ns support is implemented sanely AFAICT, given what it's aiming to accomplish. There's lots of vars in the session that one might want to customize on a per-project basis, and that tools might want to know the value of. I don't see any reason to special-case *ns*. This is one of the rare times where I'd say that a tool's best option is to use eval.

Comment by Bozhidar Batsov [ 27/Aug/14 10:09 AM ]

While I'd normally agree, the problem is that I'd have to rework cider's init in a bit awkward manner:

  • run describe session to obtain the REPL capabilities and version info
  • its callback should then do eval for ns
  • its callback should then spawn the REPL buffer

While I can certainly do this, chaining callbacks just to get some bootstrap info seems suboptimal to me. Ideally all bootstrap information
should be obtainable with a single request.
You can see the code in question here https://github.com/clojure-emacs/cider/blob/master/nrepl-client.el#L434

I can't imagine any other var value that a similar tool would like to know while bootstrapping. Obviously once you're up and running using eval is the natural solution.





[NREPL-44] Expose JMX MBean to provide list of available nREPL endpoints Created: 06/Aug/13  Updated: 19/Aug/14

Status: Open
Project: tools.nrepl
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Enhancement Priority: Trivial
Reporter: Chas Emerick Assignee: Chas Emerick
Resolution: Unresolved Votes: 0
Labels: None


 Description   

In a development environment, one often has many nREPL servers running, sometimes more than one per project. This means that it's sometimes difficult to keep track of which ports are associated with which projects / processes, and existing per-project REPL tracking mechanisms (e.g. Leiningen/reply's repl-port file) are generally not up the job.

It would be great if nREPL exposed a JMX MBean that provided information on each active nREPL server, what URL(s) they'll respond to, and perhaps other details (what middleware is installed on each, etc). Clients could then use JMX to discover all of the nREPL servers on a given host, and present that information in tool-appropriate 'connect' dialogs, etc.



 Comments   
Comment by Alan Effrig [ 08/Aug/13 7:50 PM ]

How do you envision clients discover which processes have nREPL servers? How would it work in practice from the client's point of view? Would the client be responsible for knowing the JMX port & associated configuration? Do you envision this feature applying mainly to clients on the local machine or to any number of hosts?

When I've worked with JMX, part of the battle is knowing the proper port and associated JMX configuration for each process so a client knows how to connect, especially with a variety of processes on a given host. It is even more problematic in the cloud with dozens of servers. And then there is the complication that locally one can sometimes use the Attach API, a mechanism that differs from how JMX is accessed remotely. At the risk of thinking too much, is there any other standard discovery mechanism that might be appropriate to share the JMX port & configuration with potential clients? Would some sort of multicast/cluster mechanism work here?





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