SQL AST: min/max/avg improvements (#587)Co-authored-by: Markus Staab <[email protected]>

* SQL AST: min/max/avg improvements

Fix the avg return type extension using the following rules for its
return value:

* `null` if the input is only null.
* `numeric-string` if non-null inputs are only integers.
* `float` if _any_ non-null input is a string.

Put min/max in their own return type extension, since their behavior is
sufficiently different from avg. They return the input type, but if any
input is a string, then the return value is stringified.

* Fix avg/min/max due to confusion with ifnull

* min/max do not change any types
* avg converts ints to numeric-string and strings to floats

* Add test cases for non-empty/falsy-string

* Update pdo-mysql cache

* Update tests/sqlAst/data/sql-ast-narrowing.php

---------

Co-authored-by: Markus Staab <[email protected]>

Author: hemberger

src/SqlAst/AvgReturnTypeExtension.php

@@ -4,16 +4,20 @@
 
 namespace staabm\PHPStanDba\SqlAst;
 
+use PHPStan\Type\Accessory\AccessoryNumericStringType;
+use PHPStan\Type\IntersectionType;
+use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\UnionType;
 use SqlFtw\Sql\Expression\BuiltInFunction;
 use SqlFtw\Sql\Expression\FunctionCall;
 
 final class AvgReturnTypeExtension implements QueryFunctionReturnTypeExtension
 {
     public function isFunctionSupported(FunctionCall $expression): bool
     {
-        return \in_array($expression->getFunction()->getName(), [BuiltInFunction::AVG, BuiltInFunction::MIN, BuiltInFunction::MAX], true);
+        return \in_array($expression->getFunction()->getName(), [BuiltInFunction::AVG], true);
     }
 
     public function getReturnType(FunctionCall $expression, QueryScope $scope): ?Type
@@ -25,8 +29,38 @@ public function getReturnType(FunctionCall $expression, QueryScope $scope): ?Typ
         }
 
         $argType = $scope->getType($args[0]);
-        $numberType = $argType->toNumber();
 
-        return TypeCombinator::addNull($numberType);
+        if ($argType->isNull()->yes()) {
+            return $argType;
+        }
+        $argType = TypeCombinator::removeNull($argType);
+
+        if ($argType instanceof UnionType) {
+            $newTypes = [];
+            foreach ($argType->getTypes() as $type) {
+                $newTypes[] = $this->convertToAvgType($type);
+            }
+            $newType = TypeCombinator::union(...$newTypes);
+        } else {
+            $newType = $this->convertToAvgType($argType);
+        }
+
+        return TypeCombinator::addNull($newType);
+    }
+
+    private function convertToAvgType(Type $argType): Type
+    {
+        if ($argType->isInteger()->yes()) {
+            return new IntersectionType([
+                new StringType(),
+                new AccessoryNumericStringType(),
+            ]);
+        }
+
+        if ($argType->isString()->yes()) {
+            return $argType->toFloat();
+        }
+
+        return $argType;
     }
 }

src/SqlAst/MinMaxReturnTypeExtension.php

@@ -0,0 +1,31 @@
+<?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 MinMaxReturnTypeExtension implements QueryFunctionReturnTypeExtension
+{
+    public function isFunctionSupported(FunctionCall $expression): bool
+    {
+        return \in_array($expression->getFunction()->getName(), [BuiltInFunction::MIN, BuiltInFunction::MAX], true);
+    }
+
+    public function getReturnType(FunctionCall $expression, QueryScope $scope): ?Type
+    {
+        $args = $expression->getArguments();
+
+        if (1 !== \count($args)) {
+            return null;
+        }
+
+        $argType = $scope->getType($args[0]);
+
+        return TypeCombinator::addNull($argType);
+    }
+}

src/SqlAst/QueryScope.php

@@ -69,6 +69,7 @@ public function __construct(Table $fromTable, array $joinedTables)
             new IsNullReturnTypeExtension(),
             new AbsReturnTypeExtension(),
             new RoundReturnTypeExtension(),
+            new MinMaxReturnTypeExtension(),
         ];
     }