prints should accept an optional extra param "then" or similar to validate the result of the provided function #994

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1. kevmoo

   added

   type-enhancementA request for a change that isn't a bugA request for a change that isn't a bug

   on Mar 2, 2019
2. grouma commented on Mar 4, 2019

   

   grouma

   on Mar 4, 2019

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   I'm not sure I follow this request. Can you elaborate with a brief example?
3. kevmoo commented on Mar 4, 2019

   

   kevmoo

   on Mar 4, 2019

   Last edited by lrhn

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   expect(() => process(1,2,3), prints('hello'));

   Fine, but what if I want to check a thrown exception or the result?

   expect(() => process(1,2,3), prints('wth, yo?').then(throwsArgumentError));
4. lrhn commented on Mar 4, 2019

   

   lrhn

   on Mar 4, 2019

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   This is a reasonable request since prints is not checking the result, but checking side-effects created during the evaluation. You can have many side effects, and still have one result afterward. Other matchers check the result (value or thrown) and there can only be one of those.

   Maybe there could be a SideEffectMatcher with an optional Matcher then(Matcher) method and perhaps an SideEffectMatcher and(SideEffectMatcher) for chaining multiple side effects. Example:

   abstract class SideEffectMatcher implements Matcher {
     SideEffectMatcher and(SideEffectMatcher nextSideEffect);
     Matcher then(dynamic result);
   }

   Then prints would be a SideEffectMatcher.
5. kevmoo commented on Mar 4, 2019

   

   kevmoo

   on Mar 4, 2019

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   @lrhn – SGTM!
6. natebosch commented on Mar 5, 2019

   

   natebosch

   on Mar 5, 2019

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   Does this work today with allOf?

   expect(() => process(1,2,3), allOf(prints('hello'), throwsArgumentError));

   Would the side effects need to be ordered?
7. kevmoo commented on Mar 5, 2019

   

   kevmoo

   on Mar 5, 2019

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   Tried that. It doesn't work.
8. natebosch commented on Mar 5, 2019

   

   natebosch

   on Mar 5, 2019

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   We could consider trying to make the allof version work, though taking a look at the implementation that most likely means that the function would get run twice - once to check the prints and once to check the throwsArgumentError.

   Making multiple matchers cooperate and only run a Function() once does not look immediately feasible to me.

   If it's acceptable to let the function run once per matcher I can run with that. Otherwise we'll likely need a separate approach and provide a different utility.

   var printCapture = PrintCapture();
   expect(printCapture.wrap(() => process(1,2,3)), throwsArgumentError);
   expect(printCapture.captured, contains('hello'));
9. kevmoo commented on Mar 5, 2019

   

   kevmoo

   on Mar 5, 2019 via email

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   That's not a bad idea, Nate.

   …

   On Tue, Mar 5, 2019 at 10:02 AM Nate Bosch ***@***.***> wrote: We could consider trying to make the allof version work, though taking a look at the implementation that most likely means that the function would get run twice - once to check the prints and once to check the throwsArgumentError. Making multiple matchers cooperate and only run a Function() once does not look immediately feasible to me. If it's acceptable to let the function run once per matcher I can run with that. Otherwise we'll likely need a separate approach and provide a different utility. var printCapture = PrintCapture();expect(printCapture.wrap(() => process(1,2,3)), throwsArgumentError);expect(printCapture.captured, contains('hello')); — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#994 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABCivkDqmbtzZWjYGJMeRY6fdvzsuokks5vTrFBgaJpZM4baMTZ> .