[Seaside-dev] Grease on Pharo7: streams

[Paul DeBruicker]

Hi Johan,


I just downloaded Pharo 7 (on the mac, 64bit image/vm) to try this out
because I was wondering if it was filling with spaces or null characters and
inspecting


(ReadWriteStream on: (String new: 4096)) contents


gave an empty string.  Could something else cause the 4096 char string? 






Johan Brichau-2 wrote
> Hi all,
> 
> There have been a number of changes to the ReadWriteStream implementation
> in Pharo 7 that break Grease stream tests:
> https://travis-ci.org/SeasideSt/Grease/jobs/406766720
> <https://travis-ci.org/SeasideSt/Grease/jobs/406766720>
> I think there is both an issue in Grease for Pharo and in Pharo 7 itself.
> 
> * The most important issue is that the following expression returns a
> different result on Pharo 7 when compared with earlier versions:
> 	
> 	(ReadWriteStream on: (String new: 4096)) contents
> 
> On Pharo 6, this returns an empty string.
> On Pharo 7, this returns a string with 4096 white space chars.
> 
> I’m inclined to say that Pharo 7 behavior is correct.
> I read through the ANSI document and `contents` should return the future
> sequences as well… which effectively means returning all those empty
> chars.
> I’m a bit in doubt why this has been different all that time… hence my
> email.
> 
> The core of the issue is that GRPharoPlatform>>readWriteCharacterStream is
> `ReadWriteStream on: (String new: 4096)`, hence a String instance with a
> lot of spaces ;)
> In GRGemStonePlatform, the readWriteStream is initialized on an empty
> string.
> In GRSqueakPlatform, the RWBinaryOrTextStream class is used on ‘ByteArray
> new: 4096’.
> 
> Changing the implementation of GRPharoPlatform>>readWriteCharacterStream
> to `ReadWriteStream on: String new` fixes most of the tests.
> 
> * The next issue is that `ReadWriteStream>>contents` has been changed in
> https://github.com/pharo-project/pharo/commit/9e442addff3790af0c78dbc73f1f349de8a4ad03#diff-ba7cc7962a4a22468a18b31fe75ada04
> <https://github.com/pharo-project/pharo/commit/9e442addff3790af0c78dbc73f1f349de8a4ad03#diff-ba7cc7962a4a22468a18b31fe75ada04>
> This means that:
> 
> | stream |
> stream := GRPlatform current readWriteCharacterStream.
> stream
> 	nextPutAll: 'abc';
> 	reset.
> self assert: stream contents = 'abc’.
> 
> This is no longer true in Pharo 7.
> ANSI docs says that `reset` should only reset the pointer position and
> thus the future sequences on the stream should still be returned after
> resetting. 
> Reverting the change in the commit, also fixes that test.
> It’s unclear why that change was made though, so I’ll try to talk to
> someone at Pharo.
> 
> Would be nice to hear other’s thoughts.
> 
> Cheers
> Johan
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