From b0b3c9287e29bed3f18712fedea95f0eca74038d Mon Sep 17 00:00:00 2001
From: Matthew Brown <github@muglug.com>
Date: Sat, 17 Mar 2018 19:03:46 -0400
Subject: [PATCH] Fix array_key_exists calls on possibly undefined objectlike

---
 .../Statements/Expression/AssertionFinder.php | 34 +++++++++++++++++
 src/Psalm/Type/Reconciler.php                 | 10 ++++-
 tests/ArrayAssignmentTest.php                 | 38 +++++++++++++++++++
 3 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/src/Psalm/Checker/Statements/Expression/AssertionFinder.php b/src/Psalm/Checker/Statements/Expression/AssertionFinder.php
index dbf789f35..9bbd35738 100644
--- a/src/Psalm/Checker/Statements/Expression/AssertionFinder.php
+++ b/src/Psalm/Checker/Statements/Expression/AssertionFinder.php
@@ -875,6 +875,26 @@ class AssertionFinder
             if ($first_var_name) {
                 $if_types[$first_var_name] = $prefix . 'callable';
             }
+        } elseif (self::hasArrayKeyExistsCheck($expr)) {
+            $array_root = isset($expr->args[1]->value)
+                ? ExpressionChecker::getArrayVarId(
+                    $expr->args[1]->value,
+                    $this_class_name,
+                    $source
+                )
+                : null;
+
+            if ($first_var_name === null && isset($expr->args[0]->value)) {
+                if ($expr->args[0]->value instanceof PhpParser\Node\Scalar\String_) {
+                    $first_var_name = '"' . $expr->args[0]->value->value . '"';
+                } elseif ($expr->args[0]->value instanceof PhpParser\Node\Scalar\LNumber) {
+                    $first_var_name = (string) $expr->args[0]->value->value;
+                }
+            }
+
+            if ($first_var_name !== null && $array_root) {
+                $if_types[$array_root . '[' . $first_var_name . ']'] = $prefix . 'array-key-exists';
+            }
         }
 
         return $if_types;
@@ -1263,4 +1283,18 @@ class AssertionFinder
 
         return false;
     }
+
+    /**
+     * @param   PhpParser\Node\Expr\FuncCall    $stmt
+     *
+     * @return  bool
+     */
+    protected static function hasArrayKeyExistsCheck(PhpParser\Node\Expr\FuncCall $stmt)
+    {
+        if ($stmt->name instanceof PhpParser\Node\Name && $stmt->name->parts === ['array_key_exists']) {
+            return true;
+        }
+
+        return false;
+    }
 }
diff --git a/src/Psalm/Type/Reconciler.php b/src/Psalm/Type/Reconciler.php
index 51d4be0d5..4eb57cc20 100644
--- a/src/Psalm/Type/Reconciler.php
+++ b/src/Psalm/Type/Reconciler.php
@@ -176,7 +176,7 @@ class Reconciler
                 return Type::getMixed();
             }
 
-            if ($new_var_type === 'isset' || $new_var_type === '!empty') {
+            if ($new_var_type === 'isset' || $new_var_type === '!empty' || $new_var_type === 'array-key-exists') {
                 return Type::getMixed();
             }
 
@@ -205,7 +205,7 @@ class Reconciler
                 return $existing_var_type;
             }
 
-            if ($new_var_type === '!isset') {
+            if ($new_var_type === '!isset' || $new_var_type === '!array-key-exists') {
                 return Type::getNull();
             }
 
@@ -489,6 +489,12 @@ class Reconciler
             return $existing_var_type;
         }
 
+        if ($new_var_type === 'array-key-exists') {
+            $existing_var_type->possibly_undefined = false;
+
+            return $existing_var_type;
+        }
+
         if ($new_var_type === '^!empty') {
             $existing_var_type->removeType('null');
             $existing_var_type->removeType('false');
diff --git a/tests/ArrayAssignmentTest.php b/tests/ArrayAssignmentTest.php
index 4a9433179..1558c6e9e 100644
--- a/tests/ArrayAssignmentTest.php
+++ b/tests/ArrayAssignmentTest.php
@@ -850,6 +850,18 @@ class ArrayAssignmentTest extends TestCase
                         echo $a[0];
                     }',
             ],
+            'possiblyUndefinedArrayAccessWithArrayKeyExists' => [
+                '<?php
+                    if (rand(0,1)) {
+                      $a = ["a" => 1];
+                    } else {
+                      $a = [2, 3];
+                    }
+
+                    if (array_key_exists(0, $a)) {
+                        echo $a[0];
+                    }',
+            ],
         ];
     }
 
@@ -929,6 +941,32 @@ class ArrayAssignmentTest extends TestCase
                     }',
                 'error_message' => 'InvalidPropertyAssignmentValue',
             ],
+            'possiblyUndefinedArrayAccessWithArrayKeyExistsOnWrongKey' => [
+                '<?php
+                    if (rand(0,1)) {
+                      $a = ["a" => 1];
+                    } else {
+                      $a = [2, 3];
+                    }
+
+                    if (array_key_exists("a", $a)) {
+                        echo $a[0];
+                    }',
+                'error_message' => 'PossiblyUndefinedGlobalVariable',
+            ],
+            'possiblyUndefinedArrayAccessWithArrayKeyExistsOnMissingKey' => [
+                '<?php
+                    if (rand(0,1)) {
+                      $a = ["a" => 1];
+                    } else {
+                      $a = [2, 3];
+                    }
+
+                    if (array_key_exists("b", $a)) {
+                        echo $a[0];
+                    }',
+                'error_message' => 'PossiblyUndefinedGlobalVariable',
+            ],
         ];
     }
 }