Doctrine2 ORM strategy for quoting all identifiers by default.

EagerQuoteStrategy.php

<?php
namespace Doctrine\ORM\Mapping;

use Doctrine\ORM\Mapping\ClassMetadata;
use Doctrine\DBAL\Platforms\AbstractPlatform;

/**
 * A set of rules for determining the physical column, alias and table quotes
 */
class EagerQuoteStrategy implements QuoteStrategy
{
    /**
     * {@inheritdoc}
     */
    public function getColumnName($fieldName, ClassMetadata $class, AbstractPlatform $platform)
    {
        return $platform->quoteIdentifier($class->fieldMappings[$fieldName]['columnName']);
    }

    /**
     * {@inheritdoc}
     */
    public function getTableName(ClassMetadata $class, AbstractPlatform $platform)
    {
        return $platform->quoteIdentifier($class->table['name']);
    }

    /**
     * {@inheritdoc}
     */
    public function getSequenceName(array $definition, ClassMetadata $class, AbstractPlatform $platform)
    {
        return $platform->quoteIdentifier($definition['sequenceName']);
    }

    /**
     * {@inheritdoc}
     */
    public function getJoinColumnName(array $joinColumn, ClassMetadata $class, AbstractPlatform $platform)
    {
        return $platform->quoteIdentifier($joinColumn['name']);
    }

    /**
     * {@inheritdoc}
     */
    public function getReferencedJoinColumnName(array $joinColumn, ClassMetadata $class, AbstractPlatform $platform)
    {
        return $platform->quoteIdentifier($joinColumn['referencedColumnName']);
    }

    /**
     * {@inheritdoc}
     */
    public function getJoinTableName(array $association, ClassMetadata $class, AbstractPlatform $platform)
    {
        return $platform->quoteIdentifier($association['joinTable']['name']);
    }

    /**
     * {@inheritdoc}
     */
    public function getIdentifierColumnNames(ClassMetadata $class, AbstractPlatform $platform)
    {
        $quotedColumnNames = array();

        foreach ($class->identifier as $fieldName) {
            if (isset($class->fieldMappings[$fieldName])) {
                $quotedColumnNames[] = $this->getColumnName($fieldName, $class, $platform);

                continue;
            }

            // Association defined as Id field
            $joinColumns            = $class->associationMappings[$fieldName]['joinColumns'];
            $assocQuotedColumnNames = array_map(
                function ($joinColumn) use ($platform)
                {
                    return $platform->quoteIdentifier($joinColumn['name']);
                },
                $joinColumns
            );

            $quotedColumnNames = array_merge($quotedColumnNames, $assocQuotedColumnNames);
        }

        return $quotedColumnNames;
    }

    /**
     * {@inheritdoc}
     */
    public function getColumnAlias($columnName, $counter, AbstractPlatform $platform, ClassMetadata $class = null)
    {
        // 1 ) Concatenate column name and counter
        // 2 ) Trim the column alias to the maximum identifier length of the platform.
        //     If the alias is to long, characters are cut off from the beginning.
        // 3 ) Strip non alphanumeric characters
        // 4 ) Prefix with "_" if the result its numeric
        $columnName = $columnName . $counter;
        $columnName = substr($columnName, -$platform->getMaxIdentifierLength());
        $columnName = preg_replace('/[^A-Za-z0-9_]/', '', $columnName);
        $columnName = is_numeric($columnName) ? '_' . $columnName : $columnName;

        return $platform->getSQLResultCasing($columnName);
    }
}

Fix:

http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/basic-mapping.html#quoting-reserved-words

Identifier Quoting does not work for join column names or discriminator column names unless you are using a custom QuoteStrategy.

public function getJoinColumnName(array $joinColumn, ClassMetadata $class, AbstractPlatform $platform): string
{
    return $joinColumn['name'];
}

public function getReferencedJoinColumnName(
     array $joinColumn,
     ClassMetadata $class,
     AbstractPlatform $platform
): string {
    return $joinColumn['referencedColumnName'];
}