Ruby

When accessing elements from arrays or hashes, do not put spaces between the receiver name and the opeining brackets as it can make the code ambigous to read.

Using plaintext to render view is error prone and very unmaintanable. Prefer using templates instead of rendering inline text.

Instead of generating fragments of SQL statements within ActiveRecord#where, use it by passing in conditions as a Hash.

enumerator, rational, complex and thread need not be required, since they can be directly used in the program.

No # rubocop: enable was found in the source code after the # rubocop: disable comment. Since DeepSource respects issue silencing rules laid out by Rubocop, all issues in this file after the disable statement will be silenced, and issues will

Literals used in conditions are pointless, as the programmer already knows if the condition will evaluate to true or false.

Prefer has_many :through to has_and_belongs_to_many. Using has_many :through allows additional attributes and validations on the join model.

For transforming an enumerable into a hash where the values are the original elements, Rails provides the index_with method.

Error classes must inherit from RuntimeError instead.

By default, Rails production environments use the :info log level. At the :info log level, Rails.logger.debug statements do not result in log output.

However, Ruby must eagerly evaluate interpolated string arguments passed as method arguments. Passing a block to Rails.logger.debug prevents costly evaluation of interpolated strings when no output would be produced anyway.

Self-assignment branches should be avoided as they are inefficient, unmaintanable and lack reability. Instead it is recommended to use single line conditionals if you need to make assignments.

The %q syntax is used to define a string literal with single quotes. It is unnecessary when the string does not contain any single quotes or when you want to use double quotes instead.

For example, %q{Hello world} is equivalent to 'Hello world', but %q{Hello's world} is necessary to avoid having to escape the single quote character: 'Hello's world'.

If you don't need to use single quotes or want to use double quotes, you can use other string literal syntaxes such as %{} or "".

For example, %"Hello world" is equivalent to "Hello world", and %{Hello world} is also equivalent to "Hello world".

Avoid bubbling up exceptions with useless rescues (which only re-raise the errors) in your code as they are inefficient and can make the control flow difficult to understand.

In case you want to return nil from a case body, it is better to return it explicitly. Otherwise the intent of the code may seem ambiguous.

Calling require_relative with the path of the file it was called from doesn't perform any meaningful action since the file being executed is already in the LOAD_PATH.

Prefer passing conditions to where and where.not as a hash over using fragments of SQL.

Prefer Ruby’s comparison operators over ActiveSupport’s Array#inquiry, and String#inquiry.

Classes implementing mailing functionality (inheriting from ActionMailer::Base or ApplicationMailer) should be named with a Mailer suffix.

When you want to limit a value to a certain range, prefer using Comparable#clamp intead of combinations of min/max and conditionals.

Avoid using git ls-files to produce lists of files. Downstreams often need to build your package in an environment that does not have git (on purpose). Instead, use some pure Ruby alternatives, like Dir or Dir.glob.