Hello 🙂

Hello :D

What’s the recommended way to validate input in a macro? Say I expect a map with one key-value pair. Do I use conditionals and throw an error or is there a better way?

Can you implement a function iterate* of your own version, not using clojure.lang.Iterate/create?

And does yours work well with (take 10 (drop 100000000 (iterate* inc 1)))?

how to invoke method .whereEqualTo in class Query which is already extended in here (com.google.cloud.firestore CollectionReference)

I would check the java docs for whatever you are doing, my guess is whereEqualTo is a java varargs methods, which would mean you need to put the varargs in to an array

https://googleapis.github.io/google-cloud-java/google-cloud-clients/apidocs/com/google/cloud/firestore/Query.html#whereEqualTo-java.lang.String-java.lang.Object- it is a varargs

actually it looks like that error is coming from inside the google firestore code, likely because of a depedency versioning conflict

Can anyone guide me to some example of how to use prepl? Google is not much help and the API documentation refers to parameters, I do not know how to configure, so some working example would be very helpful. I am not going to use it for anything special, yet, just experimentation.

I’m going to write something up soon, just haven’t gotten to it

Can anyone recommend a good current (2017 or newer) book or detailed guide on web development with Clojure? Since there's no Rails or Phoenix for Clojure, it's hard to know which tools and libraries are ideal for general webdev.

(or is my old 2014 Web Development With Clojure book still relevant?)

I don't have any recommendations, but given what I've found when reading about this stuff, I'd say that the fundamentals haven't changed a lot (Clojure hasn't changed much since 2014), only the popular frameworks

I guess my concern is that since I'll be learning a lot of new things, I don't want to invest energy on a component that's going out of style. Just hoping to find a set of tools that will last a couple/few years

Reagent seems to be the current de jour react framework (with reframe supporting), and fulcro seems to be the other big name in frameworks

ok, thanks. I'll start looking there

If you want to try fulcro, this is the spot to give it a go: http://book.fulcrologic.com/

Oh super, thank you

@michael_teter there's also http://www.luminusweb.net/ , a "web framework" which is more like an opinionated set of libraries making up a proper web service

consider it a great starting kit

the documentation is pretty good as well

Yeah, these days I use luminus + re-frame to set up a basic web app shell and go from there.

i would initially leave out re-frame, it's a world in itself that might distract, depending on what you want to achieve

Ok, if Luminus is popular/relevant, and its website promotes the book I already own, then perhaps I'll just start with the book despite its age 🙂

luminus is very stable

has been around for years

I don't need front end so much right now, so if I understand correctly that's where re-frame would be involved

Right, re-frame is front-end.

re-frame is react on steroids

Thanks all.

@michael_teter It depends what you need. If you want to create a web site, I’d go to Luminus. If you want to go for an API service I’d got for https://github.com/duct-framework/duct

Thanks @lukas.rychtecky . I'm not doing an API, at least not at the moment. But I'll put duct in my save-list 🙂

how do people generally new up maps for tests

so if i have a function that accepts a map as a parameter and accesses various keys

and i want to then feed in values from a test

i’m just manually creating the maps in the tests at the moment

but there’s no code completion so i end up flipping between the two files manually generating the map

feels a bit clunky

i was going to have a go at clojure spec to generate some values

i’m used to a typed language, java kotlin etc

when as i’m creating it, intellij suggests parameters for me

@christopher.paul in my deftest body I generally let-bind the arguments to the function I'm testing.

i mean that if i have a function that accepts a map

its hard to then create the map for the test

but maybe i shouldn’t be passing maps into functions

i’ve posted some data to an endpoint as json

i’m then doin g alittle manipulating and sending it somwhere else

so i want to test the manipulation is right, at the moment maps are being passed around

clojure spec gen is definitely a solid approach

yea that’s what i’m leaning towards

Yeah, if you're trying to test out a ton of different values, spec is solid.

https://clojure.github.io/spec.alpha/clojure.spec.test.alpha-api.html#clojure.spec.test.alpha/check

Check out the exercise-fn fn I meant to say the check fn

It can gen args based on a fn spec and validate that your constraints hold for all n invocations

W.r.t passing maps into functions, I've found that to be the best approach for having maintainable code, and the openness of clojure maps makes them great for extensibility.

so if i have a function that accepts a map

and returns another

i’m trying to find the best way to assert that the mapping has been done correctly

in java tdd i’d create an input object and verify an output object

not sure whta the equivalent is in the lisp world

I think that's what the link @cjsauer posted helps with.

I'm not doing generative testing, so in my (deftest test-foo... form I have a let binding that defines my input and I have test assertions that the output of the function matches whatever shape I wanted.

yea that’s what i’ve been doing so far

but feel like i’m missing a trick

where spec would help me by generating all of the input data and validating the output shape, I'm doing that by hand.

i probably need to get underneath spec

spec examples all have ::keys

It definitely sounds like spec will line up more with what you're looking for.

does that mean that the map also needs to have ::key?

Or rather, generative testing is what you're looking for, and spec can do that.

(def person {:firstname “chris”})

does that mean i can only use spec if the keys are :: ?

I believe what you're after is the :fn argument to fdef. It's the "glue" between input and output, it relates them via predicates.

:fn A spec of the relationship between args and ret - the
  value passed is {:args conformed-args :ret conformed-ret} and is
  expected to contain predicates that relate those values

A ::key expands into a namespace qualified key.

So if you had a person namespace, and in it you did (def person {::firstname "chris"}) that would expand into {:person/firstname "chris"}

>does that mean i can only use spec if the keys are :: ? No, spec can verify unqualified keywords as well

Maybe said more concisely, the :: expands into :namespace/

hmm

i guess i need to just read up on spec

i sort of see how it can generate input and validate output

but it seems like it will validate the shape but not the contents

but maybe that’s all it’s meant to do

Based on the way I've heard spec talked about, I believe it was designed to allow validating contents.

so if the thing it returns has a list property that is ok to be empty

it might not be ok for itto be empty based on the input it was given

That seems to be Rich's thing about spec vs statically typed languages: statically typed languages can't tell you about the content in a rich way, only in a vague shape way.

sorry i need to read mor about spec, thanks for your help

:thumbsup:

I'd start with the spec guide: https://clojure.org/guides/spec And then you can take a look at test.check: https://github.com/clojure/test.check There are some good generative testing examples in there.

ok

Generative testing works really well when the input and output are related by some invariant. Sorting for example, the output better be monotonically increasing/decreasing, or we've violated the invariant. Or e.g. a full-name function: the output better contain both first and last name somewhere in the output string. Functions that are map -> map might be more difficult to test via invariants due to their high degree of dimensionality; it really depends on what the function is doing...trying to test it generatively may illuminate design flaws, however, and help you decomplect things.

yea map to map is what i’m getting at

its easy to verify the shapes of inputs and outputs, but probablly better the examine the results in specific tests

otherwise it feels like the spec would get really complex

(deftest my-macro-invalid-bindings-test
  (testing "my-macro throws error with invalid bindings"
    (is (thrown? IllegalArgumentException
                 (my-macro [] {})))
    (is (thrown? IllegalArgumentException
                 (my-macro [x] {x x})))))

I think I did it by using eval on the form

It now runs but it’s throwing a ComplierException now

@jayzawrotny That's on 1.10? Macro-expanding errors are wrapped in CompilerException in order to add all the location/phase data etc.

Yeah 1.10

Wait, I mean

It would be nice if thrown? checked both the main exception and the cause. I'll add that to the clojure.test design wiki page that just got created.

(eval `(my-macro [] {}))

this was the subject of the discussion on clojure ml yesterday

and https://dev.clojure.org/jira/browse/CLJ-2458

still deciding what, if anything, to do about it

I added a note to the clojure.test page about it. I'll link to that issue.

I have created variant assert-exprs to thrown? to look at cause in some cases. Checking both seems weird to me, but I guess is a viable alternative

Is there any discussion of the performance impact of tap> when there's no active taps?

do you mean if no taps are ever added or if all active taps have been removed?

seems no problem? the tap loop isn't started up in the former case and it will remain blocked if the tapq is empty?

both

(defonce ^:private tap-loop
  (delay
   (doto (Thread.
          #(let [t (.take tapq)

Cool, I've just been wondering about the viability of using tap> in production to get on-demand monitoring of data pipelines and such

And the documentation isn't really clear about whether this is primarily targeted towards dev-time use cases or not

I think tap> will always cost one add+take from an java.util.concurrent.ArrayBlockingQueue, even with no active taps

It's a non-blocking queue, isn't it?

From the docs "Will not block."

ah yes. the values will go into that queue. i confused the tapq for values and the tapset for taps

It uses .offer to put, so it will drop beyond 1024 items and never block

I see

Thanks

Created a solution for

(is (thrown? (eval `(my-macro [] {}))))

(is (thrown-in-macro? IllegalArgumentException `(my-macro [] {})))

If you use Throwable->map instead of datafy, it'll run on Clojure 1.9 I believe? (when was that introduced)