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[java] Fix #6692: ForLoopCanBeForeach detect i = i + 1 update form#6727

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UncleOwen merged 4 commits into
pmd:mainfrom
qwerty7878:fix/for-loop-can-be-foreach-assign-increment
May 31, 2026
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[java] Fix #6692: ForLoopCanBeForeach detect i = i + 1 update form#6727
UncleOwen merged 4 commits into
pmd:mainfrom
qwerty7878:fix/for-loop-can-be-foreach-assign-increment

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@qwerty7878

@qwerty7878 qwerty7878 commented May 28, 2026 •
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Describe the PR

Fix a false-negative in the ForLoopCanBeForeach rule where a for loop using i = i + 1 (or i = 1 + i) as the update expression was not detected as convertible to a foreach loop, even though it is semantically identical to i++ or i += 1.
Added a new helper method asIEqualIPlusOne to handle the direct assignment pattern.

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  • Added unit tests for fixed bug/feature
  • Passing all unit tests
  • Complete build ./mvnw clean verify passes (checked automatically by github actions)
  • Added (in-code) documentation (if needed)

@qwerty7878 qwerty7878 force-pushed the fix/for-loop-can-be-foreach-assign-increment branch from 1006269 to 9a5eb2d Compare May 28, 2026 10:13
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pmd-actions-helper Bot commented May 28, 2026 •
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Documentation Preview

Compared to main:
This changeset changes 0 violations,
introduces 0 new violations, 0 new errors and 0 new configuration errors,
removes 0 violations, 15 errors and 9 configuration errors.
There are 0 changed duplications, 0 new duplications and 0 removed duplications.
There are 0 changed CPD errors, 0 new CPD errors and 0 removed CPD errors.

Regression Tester Report

(comment created at 2026-05-31 07:51:25+00:00 for 0f36c16)

UncleOwen
UncleOwen requested changes May 30, 2026
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@UncleOwen UncleOwen left a comment

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I've left some suggestions. Otherwise, this looks good!

Comment thread .../src/main/java/net/sourceforge/pmd/lang/java/rule/bestpractices/ForLoopCanBeForeachRule.java Outdated
Comment thread .../test/resources/net/sourceforge/pmd/lang/java/rule/bestpractices/xml/ForLoopCanBeForeach.xml
Comment thread .../src/main/java/net/sourceforge/pmd/lang/java/rule/bestpractices/ForLoopCanBeForeachRule.java Outdated
@qwerty7878 qwerty7878 requested a review from UncleOwen May 30, 2026 22:20
@qwerty7878

qwerty7878 commented May 30, 2026 •
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Thank you for the review! I've addressed all the comments:

  • Reordered the condition for readability
  • Applied static imports for isReferenceToVar and isLiteralInt
  • Added test cases for i = 1 + i, i = 1 - 1, and i = somefunc(i)

UncleOwen
UncleOwen approved these changes May 31, 2026
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Thanks!

@UncleOwen UncleOwen added this to the 7.26.0 milestone May 31, 2026
@UncleOwen UncleOwen merged commit 8a740a4 into pmd:main May 31, 2026
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[java] ForLoopCanBeForeach: inconsistent detection between i += 1 and i = i + 1 update forms

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