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REPL thread management violates principle of least astonishment and is unusable with libraries that use thread-locals #4886

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scabug opened this issue Aug 7, 2011 · 4 comments
Closed

REPL thread management violates principle of least astonishment and is unusable with libraries that use thread-locals #4886

scabug opened this issue Aug 7, 2011 · 4 comments
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enhancement repl
Milestone
2.10.0

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@scabug
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scabug commented Aug 7, 2011

The Scala 2.9 REPL evaluates each line in its own thread.

This violates the principle of least astonishment, but more importantly, it makes the REPL unusable with the many libraries that rely on thread-local contexts.

For instance, many ORMs use thread-locals for session management. One cannot meaningfully use these ORMs from the REPL as a result.
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scabug commented Aug 7, 2011

Imported From: https://issues.scala-lang.org/browse/SI-4886?orig=1
Reporter: Yang Zhang (yaaang)
Affected Versions: 2.9.0-1

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scabug commented Sep 21, 2011

@paulp said:
-Yrepl-sync in 2.9.1 disables thread creation.

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scabug commented Jul 14, 2012

Christian Schlichtherle (christian_schlichtherle) said:
This just puzzled me, too:

Welcome to Scala version 2.9.2 (Java HotSpot(TM) Client VM, Java 1.7.0_05).
Type in expressions to have them evaluated.
Type :help for more information.

scala> val tl = new ThreadLocal[Int]
tl: java.lang.ThreadLocal[Int] = java.lang.ThreadLocal@3571fd

scala> tl.set(1)

scala> tl.get
res1: Int = 0

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scabug commented Jan 6, 2015

@som-snytt said:
Fair to say this was settled in 2.10, except maybe for the part about being least astonished.

@scabug scabug closed this as completed Jun 6, 2015
@scabug scabug added this to the 2.10.0 milestone Apr 7, 2017
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