Support shorthand list assignment (#50)

* Tests: add test for destructuring assignment

* Support shorthand list assignment

Author: sirbrillig

VariableAnalysis/Lib/Helpers.php

@@ -5,6 +5,25 @@
 use PHP_CodeSniffer\Files\File;
 
 class Helpers {
+  public static function findContainingOpeningSquareBracket(File $phpcsFile, $stackPtr) {
+    $tokens = $phpcsFile->getTokens();
+    $previousStatementPtr = self::getPreviousStatementPtr($phpcsFile, $stackPtr);
+    return $phpcsFile->findPrevious(T_OPEN_SHORT_ARRAY, $stackPtr - 1, $previousStatementPtr);
+  }
+
+  public static function findContainingClosingSquareBracket(File $phpcsFile, $stackPtr) {
+    $tokens = $phpcsFile->getTokens();
+    $endOfStatementPtr = $phpcsFile->findNext([T_SEMICOLON], $stackPtr + 1);
+    if (! $endOfStatementPtr) {
+      return false;
+    }
+    return $phpcsFile->findNext(T_CLOSE_SHORT_ARRAY, $stackPtr + 1, $endOfStatementPtr);
+  }
+
+  public static function getPreviousStatementPtr(File $phpcsFile, $stackPtr) {
+    return $phpcsFile->findPrevious([T_SEMICOLON, T_CLOSE_CURLY_BRACKET], $stackPtr - 1) ?: 1;
+  }
+
   public static function findContainingOpeningBracket(File $phpcsFile, $stackPtr) {
     $tokens = $phpcsFile->getTokens();
     if (isset($tokens[$stackPtr]['nested_parenthesis'])) {

VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php

@@ -446,6 +446,29 @@ protected function checkForAssignment(File $phpcsFile, $stackPtr, $varName, $cur
     return true;
   }
 
+  protected function checkForListShorthandAssignment(File $phpcsFile, $stackPtr, $varName, $currScope) {
+    $tokens = $phpcsFile->getTokens();
+    $token  = $tokens[$stackPtr];
+
+    // OK, are we within a [ ... ] construct?
+    $openPtr = Helpers::findContainingOpeningSquareBracket($phpcsFile, $stackPtr);
+    if ($openPtr === false) {
+      return false;
+    }
+
+    // OK, we're a [ ... ] construct... are we being assigned to?
+    $closePtr = Helpers::findContainingClosingSquareBracket($phpcsFile, $stackPtr);
+    $assignPtr = Helpers::isNextThingAnAssign($phpcsFile, $closePtr);
+    if ($assignPtr === false) {
+      return false;
+    }
+
+    // Yes, we're being assigned.
+    $writtenPtr = Helpers::findWhereAssignExecuted($phpcsFile, $assignPtr);
+    $this->markVariableAssignment($varName, $writtenPtr, $currScope);
+    return true;
+  }
+
   protected function checkForListAssignment(File $phpcsFile, $stackPtr, $varName, $currScope) {
     $tokens = $phpcsFile->getTokens();
     $token  = $tokens[$stackPtr];
@@ -745,6 +768,11 @@ protected function processVariable(File $phpcsFile, $stackPtr) {
       return;
     }
 
+    // OK, are we within a [...] = construct?
+    if ($this->checkForListShorthandAssignment($phpcsFile, $stackPtr, $varName, $currScope)) {
+      return;
+    }
+
     // Are we a global declaration?
     if ($this->checkForGlobalDeclaration($phpcsFile, $stackPtr, $varName, $currScope)) {
       return;

VariableAnalysis/Tests/CodeAnalysis/VariableAnalysisTest.php

@@ -541,4 +541,16 @@ public function testIgnoreUnusedRegexpIgnoresUnusedVariables() {
     ];
     $this->assertEquals($expectedWarnings, $lines);
   }
+
+  public function testAllowDestructuringAssignment() {
+    $fixtureFile = $this->getFixture('DestructuringFixture.php');
+    $phpcsFile = $this->prepareLocalFileForSniffs($this->getSniffFiles(), $fixtureFile);
+    $phpcsFile->process();
+    $lines = $this->getWarningLineNumbersFromFile($phpcsFile);
+    $expectedWarnings = [
+      4,
+      12,
+    ];
+    $this->assertEquals($expectedWarnings, $lines);
+  }
 }

VariableAnalysis/Tests/CodeAnalysis/fixtures/DestructuringFixture.php

@@ -0,0 +1,16 @@
+<?php
+function function_with_destructuring_assignment() {
+    [$a, $b] = [1, 2];
+    [$c, $d] = [3, 4]; // unused
+    echo $a;
+    echo $b;
+    echo $c;
+}
+
+function function_with_destructuring_assignment_using_list() {
+    list( $a, $b ) = [1, 2];
+    list( $c, $d ) = [3, 4]; // unused
+    echo $a;
+    echo $b;
+    echo $c;
+}