[seahal]

Graphviz generation fails and tbls omits indexes with restricted permanent connection checkout

Thank you for maintaining rails-erd.

I encountered a connection checkout compatibility issue while generating diagrams with ActiveRecord 7.2.4 and have prepared a small fix with regression tests.

Problem

With ActiveRecord.permanent_connection_checkout = :disallowed, Graphviz PDF generation raises ActiveRecord::ActiveRecordError in RailsERD::Domain::Attribute#native_type.

The tbls generator encounters the same restriction while reading indexes. Its existing rescue StandardError returns an empty array, causing index metadata to be silently omitted.

The issue also occurs with :deprecated when ActiveRecord.deprecator.behavior = :raise.

An existing connection lease can mask the problem, so reproduction requires running the affected operations without a previously leased connection.

Root cause

Both Attribute#native_type and Diagram::Tbls#indexes_payload call Model.connection, which may perform an implicit permanent connection checkout.

ActiveRecord 7.2 introduced configuration to deprecate or disallow this behavior.

Proposed fix

Use model.connection_pool.with_connection at the two metadata access sites.

This scopes connection usage to the operation and avoids version-specific branches. The pool API is also available in ActiveRecord 7.0.

Verification

I reproduced the problem using independent SQLite processes on ActiveRecord 7.2.4, testing all six combinations of:

• Checkout mode: true, :deprecated, :disallowed
• Deprecation behavior: :raise, logging collector

Before the fix:

• :deprecated with :raise prevented Graphviz generation and caused tbls indexes to be omitted.
• Both :disallowed configurations produced the same failures.
• :deprecated with logging allowed generation but emitted a deprecation warning.

After the fix, Graphviz generated PDFs with valid signatures and tbls preserved the unique index in all six configurations, without connection deprecation warnings.

Three regression tests also confirmed the original failure: one assertion failure and two errors without the fix on ActiveRecord 7.2.4.

The repaired implementation passes the full test suite on the locally tested ActiveRecord versions.

References

• [ActiveRecord 7.2 connection API](https://api.rubyonrails.org/v7.2/classes/ActiveRecord/ConnectionHandling.html#method-i-connection)
• [ActiveRecord 7.0 connection pool API](https://api.rubyonrails.org/v7.0/classes/ActiveRecord/ConnectionAdapters/ConnectionPool.html#method-i-with_connection)

Would you be open to a pull request for this approach? I'm happy to adapt the implementation or tests to the project's conventions.