rspec-let-do-blocks

RSpec: Use do...end for Multi-line let Declarations & Format Method Calls

1. Use do...end for Multi-line let: When a let or let! declaration's body spans multiple lines (e.g., defining a multi-line hash/array, or a method call with multiple arguments/lines), use the do ... end block syntax instead of curly braces { ... }.

2. Use do...end for Complex Single Lines: Even if a let body is technically a single expression, use do...end if the expression is long or complex (e.g., involves significant method chaining, complex interpolation, or nested structures) to improve readability.

3. Format Multi-line Method Calls: When the body of a let is a method call with keyword arguments or multiple arguments that make the line long, format the call across multiple lines with one argument per line, indented.

4. Prefer Ruby Hashes for JSON: When creating JSON strings within let blocks, prefer constructing them from Ruby hashes using .to_json for better readability and maintainability.

Good:

# Multi-line array
let(:ignore_patterns) do
  [
    { method: :get, path: %r{/ignored/.*} },
    { method: :post, path: %r{/other/} },
    { path: %r{/any_method/.*} }
  ]
end

# Multi-line method call with keyword args
let(:response) do
  Faraday::Response.new(
    status: 200,
    body: { data: :test }.to_json, # Construct JSON from hash
    response_headers: {
      'Content-Type' => 'application/json'
    }
  )
end

# Multi-line hash definition
let(:ignored_env) do
  { method: :get, url: URI('http://example.com/ignored/path'), body: nil }
end

# Complex single line expression
let(:ignored_with_params_cache_key) do
  "faraday_cache:#{Digest::MD5.hexdigest("#{ignored_env_with_params[:method]}:#{ignored_env_with_params[:url]}:#{ignored_env_with_params[:body]}")}"
end

Bad:

# Using { ... } for multi-line blocks
let(:ignore_patterns) { [
    { method: :get, path: %r{/ignored/.*} },
    { method: :post, path: %r{/other/} },
    { path: %r{/any_method/.*} }
  ] }

# Complex expression squeezed onto one line with { ... }
let(:ignored_with_params_cache_key) { "faraday_cache:#{Digest::MD5.hexdigest("#{ignored_env_with_params[:method]}:#{ignored_env_with_params[:url]}:#{ignored_env_with_params[:body]}")}" }

For simple single-line declarations, curly braces are acceptable.

let(:simple_value) { 123 }