Improve Config handling

[methane]

Description

This pull request refactors how connection configuration and attributes are managed during MySQL connection establishment, improving flexibility and correctness when using dynamic configuration (such as via BeforeConnect hooks). The most significant changes include removing the connector reference from mysqlConn, ensuring all connection state is sourced from the effective Config, and updating tests to verify these behaviors.

Refactoring connection configuration management:

• Removed the connector field from mysqlConn and all related references, ensuring all state (including encoded connection attributes) is accessed from the effective Config at connection time. (connection.go, packets.go, connector.go) [1] [2] [3] [4] [5]

• Moved encodedAttributes from connector to Config, and ensured it is regenerated in Config.normalize() to reflect any changes made by BeforeConnect hooks. (dsn.go, connector.go) [1] [2] [3]

• Updated connection logic to always use the latest Config values (for timeouts, dialers, logging, etc.) after normalization and hooks are applied. (connector.go) [1] [2] [3] [4]

TLS server name derivation improvements:

• Improved logic for deriving the TLS ServerName from the address, and added a tlsServerNameDerived flag to track when this is done, ensuring hooks can override it as needed. (dsn.go) [1] [2]

Test coverage for dynamic configuration:

• Added comprehensive tests to verify that BeforeConnect hooks can update timeouts, TLS settings, dialers, and connection attributes, and that these updates are correctly reflected in the established connection. (connector_test.go, dsn_test.go, packets_test.go) [1] [2] [3] [4]

Other cleanups:

• Refactored mysqlConn.initCapabilities to use its own cfg field, simplifying the method signature. (packets.go) [1] [2] [3]

These changes make the connector more robust, especially in dynamic or advanced use cases where connection parameters may be modified at runtime.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[Copilot]

🟡 Changes recommended

Hook normalization can override explicit TLS names and mishandle resolved server public keys.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Refactors connection setup to use the effective per-connection configuration after BeforeConnect.

Changes:

• Moves encoded attributes into Config.
• Uses hook-updated timeouts, dialers, TLS settings, and attributes.
• Adds dynamic configuration tests.

File summaries

File	Description
connection.go	Removes the connector reference.
connector.go	Normalizes and uses effective configuration.
connector_test.go	Tests hook-driven configuration changes.
dsn.go	Tracks derived TLS names and encoded attributes.
dsn_test.go	Updates configuration expectations.
packets.go	Reads capabilities and attributes from Config.
packets_test.go	Normalizes mock connection configuration.

Review details

• Files reviewed: 7/7 changed files
• Comments generated: 2
• Review effort level: Balanced

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📒 Files selected for processing (1)

• dsn.go

🚧 Files skipped from review as they are similar to previous changes (1)

• dsn.go

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Walkthrough

Connection setup now stores encoded attributes on Config, applies BeforeConnect changes to a cloned configuration, and uses that configuration for dialing and handshake processing. mysqlConn no longer stores a connector back-reference.

Changes

Connection configuration flow

Layer / File(s)	Summary
Config normalization and derived values dsn.go, dsn_test.go, connector_test.go	Config.normalize() stores encoded connection attributes. BeforeConnect documents the TLS ServerName requirement when Addr changes. Tests update expected normalized configuration and remove the TLS server-name regression case.
Callback-effective connection setup connector.go, connector_test.go	Connect encodes attributes after BeforeConnect and uses the effective configuration for dialing, timeouts, addresses, dialers, logging, and capability initialization. The connector no longer stores encoded attributes or a mysqlConn back-reference.
Connection capability and handshake configuration packets.go, packets_test.go	Packet handling reads configuration and encoded attributes from mysqlConn.cfg. Test connections now assign a normalized configuration directly.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Merge Risk: ⚪ Minimal · up to 80d48

Connection setup now applies normalized and callback-effective configuration values consistently through dialing and handshake processing. No concrete unresolved merge-readiness risk is identified.

Sequence Diagram(s)

sequenceDiagram
  participant Connector
  participant Config
  participant DialFunc
  participant mysqlConn
  participant MySQLServer
  Connector->>Config: apply BeforeConnect changes
  Connector->>Config: encode effective connection attributes
  Connector->>DialFunc: dial using effective timeout and address
  DialFunc->>mysqlConn: return connection
  mysqlConn->>MySQLServer: send handshake response with encoded attributes

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 6 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: improving configuration handling during connection establishment.
Description check	✅ Passed	The description accurately covers the configuration refactor, dynamic BeforeConnect behavior, TLS handling, and related tests.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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Inline comments:
In `@dsn.go`:
- Line 251: Update the TLS normalization flow around tlsServerNameDerived and
BeforeConnect: clear the previously derived server name and its flag before
invoking BeforeConnect, then derive a new name only when the callback leaves
cfg.TLS.ServerName empty. Preserve callback-provided explicit values, and add a
regression case covering a callback that sets TLS.ServerName.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Team

Run ID: 99908fdc-ef94-476d-930d-e68271885441

📥 Commits

Reviewing files that changed from the base of the PR and between 6442a52 and 1f0dac3.

📒 Files selected for processing (7)

• connection.go
• connector.go
• connector_test.go
• dsn.go
• dsn_test.go
• packets.go
• packets_test.go

💤 Files with no reviewable changes (1)

• connection.go

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

[coveralls]

coverage: 84.454% (-0.1%) from 84.551% — methane:codex/before-connect-effective-config into go-sql-driver:master