coalesce() unions only types until the first non-nullable (#519)

Author: staabm

.phpstan-dba-mysqli.cache

@@ -28,7 +28,7 @@ public function __construct(PDO $pdo)
     }
 
     /** @return PDOException|list<PDOColumnMeta>|null */
-    protected function simulateQuery(string $queryString)
+    protected function simulateQuery(string $queryString) // @phpstan-ignore-line
     {
         if (\array_key_exists($queryString, $this->cache)) {
             return $this->cache[$queryString];

.phpstan-dba-pdo-mysql.cache

@@ -13,7 +13,7 @@ final class CoalesceReturnTypeExtension implements QueryFunctionReturnTypeExtens
 {
     public function isFunctionSupported(FunctionCall $expression): bool
     {
-        return \in_array($expression->getFunction()->getName(), [BuiltInFunction::COALESCE, BuiltInFunction::IFNULL, BuiltInFunction::NULLIF], true);
+        return \in_array($expression->getFunction()->getName(), [BuiltInFunction::COALESCE], true);
     }
 
     public function getReturnType(FunctionCall $expression, QueryScope $scope): Type
@@ -28,6 +28,7 @@ public function getReturnType(FunctionCall $expression, QueryScope $scope): Type
             $results[] = $argType;
             if (!TypeCombinator::containsNull($argType)) {
                 $containsNonNullable = true;
+                break;
             }
         }
 

src/QueryReflection/PdoPgSqlQueryReflector.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace staabm\PHPStanDba\SqlAst;
+
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use SqlFtw\Sql\Expression\BuiltInFunction;
+use SqlFtw\Sql\Expression\FunctionCall;
+
+final class IfNullReturnTypeExtension implements QueryFunctionReturnTypeExtension
+{
+    public function isFunctionSupported(FunctionCall $expression): bool
+    {
+        return \in_array($expression->getFunction()->getName(), [BuiltInFunction::IFNULL, BuiltInFunction::NULLIF], true);
+    }
+
+    public function getReturnType(FunctionCall $expression, QueryScope $scope): Type
+    {
+        $args = $expression->getArguments();
+
+        $results = [];
+        foreach ($args as $arg) {
+            $argType = $scope->getType($arg);
+
+            $results[] = $argType;
+        }
+
+        return TypeCombinator::union(...$results);
+    }
+}

src/SqlAst/CoalesceReturnTypeExtension.php

@@ -51,6 +51,7 @@ public function __construct(Table $fromTable, array $joinedTables)
         $this->extensions = [
             new PositiveIntReturnTypeExtension(),
             new CoalesceReturnTypeExtension(),
+            new IfNullReturnTypeExtension(),
             new ConcatReturnTypeExtension(),
             new InstrReturnTypeExtension(),
             new StrCaseReturnTypeExtension(),