Ruby json accepts duplicate keys by keeping the last value, tolerates comment-like truncation in some cases, and can decode huge exponents to Infinity.

WebMock fails on IPv6 URLs because addresses need brackets before the port, causing invalid URI and port parsing errors in CarrierWave and SsrfFilter.

ZSH can replace Bash on Ubuntu 20.04 and adds command-line conveniences like completion, corrections, themes, and plugins.

Mixed content behavior differs when secure pages load assets over HTTPS versus HTTP, exposing browser handling of blocked or downgraded resources.

Create a Time in a fixed timezone regardless of Rails or system settings; useful for tests and API date comparisons when parsing otherwise shifts by environment.

rspec_rails with Rails 6.1 can raise WrongScopeError; upgrading the gem to 4.0.1 or later resolves the failure.

REST API design often fails on timestamps, number handling, pagination, filtering, and versioning. Consistent conventions improve interoperability and client stability.

Legacy ImageMagick installs can be kept available when the system package is unavailable by running convert and related tools in a Docker container with absolute paths.

Migrating a larger Rails app from Bootstrap 3 to 4 often breaks styles, components and helper gems; planning library upgrades and rebuilding variables reduces the pain.

Nested form records on overridden associations are not persisted unless the parent association enables autosave.

Old docker-compose versions can reject modern Compose file formats and report an unsupported version in docker-compose.yml. Upgrading to a newer Compose release resolves the mismatch.

Rails 6 Action Text provides a built-in WYSIWYG editor for rich text fields, with Trix hooks for custom toolbar buttons and attachment handling.

PostgreSQL partial indexes reduce index size and write overhead by indexing only rows that match a condition, useful for conditional uniqueness and large tables.

Deployment asset precompilation can fail with Command "webpack" not found when Yarn dependencies are missing. A bin/yarn binstub lets yarn install run during deploy.

Well-designed APIs improve adoption and maintainability for both library authors and users; Joshua Bloch presents practical guidance and examples of good and bad API design.

Custom flash types let controllers use extra redirect messages such as success, useful for Bootstrap-style alerts beyond notice and alert.

Large codebase diffs can become unreadable after migrations, renames, and mass file moves; git options help isolate moved code and reduce review noise.

Ruby can misdetect a file’s encoding; specifying it manually keeps the resulting string in the expected Encoding and avoids hidden byte conversion.

Browser memory leaks often come from forgotten listeners, timers, observers, unresolved promises, global stores, or unbounded DOM growth.

Interprocess communication in Ruby can use UNIX sockets for parent-child coordination, parallel test synchronization, and waiting for child cleanup after fork.

External notification plugins can stop delivering exceptions when DNS lookup fails, affecting Slack or Microsoft Teams alerts. Loading resolv-replace before ExceptionNotification forces Ruby DNS resolution to work reliably.

Ruby monkey patches can reuse the overridden behavior by calling super from a prepended module, letting extensions wrap existing methods instead of replacing them outright.

Blank query values are not equivalent to missing parameters in URLs: foo= is an empty string, foo is null, and /path has no key.