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PagedSeq's slice throws a NPE if it starts on a page that hasn't been computed yet #6615

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scabug opened this issue Nov 5, 2012 · 4 comments
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@scabug
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@scabug scabug commented Nov 5, 2012

Trying to take a slice of a PagedSeq that starts on a page that hasn't been computed yet throws a NullPointerException. For example, the following works as expected:

scala> import scala.collection.immutable.PagedSeq
import scala.collection.immutable.PagedSeq

scala> PagedSeq.fromStrings(List.fill(5000)("a")).slice(4095, 4096)
res0: scala.collection.immutable.PagedSeq[Char] = PagedSeq(a)

But if we start one character later in the sequence (at the beginning of the second page), we get the following:

scala> PagedSeq.fromStrings(List.fill(5000)("a")).slice(4096, 4097)
java.lang.NullPointerException
        at scala.collection.immutable.PagedSeq.slice(PagedSeq.scala:189)
        at .<init>(<console>:9)
        at .<clinit>(<console>)
        ...

The error does not occur if you force the second page to be computed (by calling toString or length, for example) before calling slice:

scala> val s = PagedSeq.fromStrings(List.fill(5000)("a"))
s: scala.collection.immutable.PagedSeq[Char] = PagedSeq(a, a, a,  ...
scala> s.slice(4096, 4097)
res2: scala.collection.immutable.PagedSeq[Char] = PagedSeq(a)
@scabug
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@scabug scabug commented Nov 5, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6615?orig=1
Reporter: Travis Brown (travisbrown)
Affected Versions: 2.9.2, 2.10.0-RC1

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@scabug scabug commented Nov 6, 2012

@jsuereth said:
Note: This isn't a blocker for 2.10.0, but we'll try to fix it in 2.10.1

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@scabug scabug commented May 23, 2013

@JamesIry said:
Not a regression in 2.10.2 and not a blocker so not a candidate for RC2

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@scabug scabug commented Jan 13, 2014

@scabug scabug closed this Jan 13, 2014
@scabug scabug added this to the 2.11.0-M8 milestone Apr 7, 2017
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