magento2: Notice: Undefined index: {{table_name}} in /var/www/html/vendor/magento/framework/Setup/Declaration/Schema/Declaration/SchemaBuilder.php on line 354

Preconditions (*)

When one module with db_schema has a constraint on another module where the table is created via Install/Upgrade Schema it leads to the error mentioned in the title. This happens on Magento version 2.4.3-p2, 2.4.4

Steps to reproduce (*)

1. Require https://github.com/mageplaza/magento-2-blog
2. Run bin/magento setup:upgrade.
3. Create a module with this db_schema.xml file:

<?xml version="1.0" ?>
<schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Setup/Declaration/Schema/etc/schema.xsd">
    <table name="test_mageplaza" comment="Test Mageplaza Blog Posts">
        <column name="project_id" xsi:type="int" nullable="false" identity="false" unsigned="true" comment="Project ID"/>
        <column name="post_id" xsi:type="int" padding="10" unsigned="true" nullable="false" comment="Post ID"/>
        <index referenceId="TEST_MAGEPLAZA_BLOG_POSTS_POST_ID" indexType="btree">
            <column name="post_id"/>
        </index>
        <constraint xsi:type="foreign" referenceId="FK_4D4A10A4534D098BDCCE6BC9C2CABAD7" table="test_mageplaza" column="project_id" referenceTable="test_project" referenceColumn="project_id" onDelete="CASCADE"/>
        <constraint xsi:type="foreign" referenceId="FK_FAF4B768352B9AD4307CC7AFD4E2932A" table="test_mageplaza" column="post_id" referenceTable="mageplaza_blog_post" referenceColumn="post_id" onDelete="CASCADE"/>
        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="project_id"/>
            <column name="post_id"/>
        </constraint>
    </table>
</schema>

1. Run bin/magento setup:upgrade.

Expected result (*)

1.Setup upgrade runs without issues

Actual result (*)

Notice: Undefined index: mageplaza_blog_post in /var/www/html/vendor/magento/framework/Setup/Declaration/Schema/Declaration/SchemaBuilder.php on line 354

Somehow Magento tries to apply the same foreign key if one module uses Install/Upgrade Schema and the other uses db_schema.xml

Additional information to reproduce the issue

1. Create a directory under app/code called Test/Module.
2. Copy the contents from https://github.com/BorisovskiP/test-module to that directory.
3. Run bin/magento setup:upgrade

Expected result:

Both tables should be created

Actual result:

Warning: Undefined array key "test_table" in /var/www/html/vendor/magento/framework/Setup/Declaration/Schema/Declaration/SchemaBuilder.php on line 354

Tested on Magento 2.4.4, PHP 8.1.4

For PHP 7.4 the message is the one from the title of this issue.

You can also test that if you comment out the contents of db_schema.xml and run setup:upgrade the test_table (defined in \Test\Module\Setup\InstallSchema) will be created, and once you revert the commented section and again run setup:upgrade the same error message will be thrown.

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Please provide Severity assessment for the Issue as Reporter. This information will help during Confirmation and Issue triage processes.

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.