rubocop-tablecop

A RuboCop plugin for table-like, condensed Ruby formatting. Enforces vertical alignment and single-line expressions where they improve readability, while avoiding RuboCop's known autocorrect bugs.

Add to your Gemfile:

gem "rubocop-tablecop"

Then run:

bundle install

Add to your .rubocop.yml:

# RuboCop 1.72+ (plugin system - recommended)
plugins:
  - rubocop-tablecop

# Or for older RuboCop versions
require:
  - rubocop-tablecop

The plugin requires RuboCop >= 1.72.

Aligns consecutive assignment statements on the = operator for improved readability.

Enabled by default: Yes

Supports autocorrect: Yes

What it does:

• Aligns consecutive assignments at the same indentation level
• Handles simple assignments (=), compound assignments (||=, &&=, +=, etc.), and constant assignments
• Skips lines containing heredocs to avoid infinite loops with other cops
• Respects Layout/LineLength configuration

Examples:

# bad
x = 1
foo = 2
barbaz = 3

# good
x      = 1
foo    = 2
barbaz = 3

# bad (compound operators)
data ||= attrs
options = default
config &&= fallback

# good
data    ||= attrs
options   = default
config  &&= fallback

Limitations:

• Skips assignments inside blocks
• Skips multi-assignment (a, b = ...)
• Skips assignments containing heredocs
• Only aligns assignments on consecutive lines at the same indentation level

Aligns contiguous single-line method definitions so their bodies start at the same column.

Enabled by default: Yes

Supports autocorrect: Yes

What it does:

• Aligns on = for endless methods
• Aligns traditional one-liners as if they had an invisible =
• Works with both instance and singleton methods
• Respects Layout/LineLength configuration

Examples:

# bad
def foo = 1
def barbaz = 2

# good
def foo    = 1
def barbaz = 2

# bad (mixed endless and traditional)
def foo = 1
def bar() 2 end

# good
def foo   = 1
def bar()   2 end

# bad (singleton methods)
def self.x = 1
def self.longer_name = 2

# good
def self.x           = 1
def self.longer_name = 2

Limitations:

• Only aligns methods on consecutive lines at the same indentation level
• Only processes single-line methods

Condenses multi-line when clauses to single lines using the then keyword and aligns them vertically.

Enabled by default: Yes

Supports autocorrect: Yes

What it does:

• Converts multi-line when clauses to single-line format with then
• Aligns then keywords across sibling when clauses for table-like appearance
• Only condenses when the result fits within Layout/LineLength
• Preserves complex bodies that shouldn't be condensed

Examples:

# bad
case foo
when 1
  "one"
when 200
  "two hundred"
end

# good
case foo
when 1   then "one"
when 200 then "two hundred"
end

# bad
case status
when :pending
  handle_pending
when :approved
  handle_approved
end

# good
case status
when :pending  then handle_pending
when :approved then handle_approved
end

What it skips:

• Multi-statement bodies
• Bodies with heredocs
• Bodies with multi-line strings
• Bodies with comments between when and body
• Complex control flow (multi-line if/case)
• Multi-statement blocks
• Cases where condensing would exceed line length

Example of what's left alone:

# left alone (multiple statements)
case foo
when 1
  do_something
  do_something_else
end

# left alone (heredoc)
case foo
when 1
  <<~MSG
    Hello
  MSG
end

Converts multi-line single-expression methods to single-line form, avoiding all the known bugs in RuboCop's Style/EndlessMethod.

Enabled by default: Yes

Supports autocorrect: Yes

What it does:

• Converts simple multi-line methods to endless method syntax (def foo = expr)
• Falls back to traditional one-liner (def foo() expr end) for methods with modifier-if/unless that call other methods
• Avoids RuboCop's Style/EndlessMethod bugs:
  • Heredoc destruction
  • Rescue clause orphaning
  • module_eval context failures
  • Modifier-if with dynamic method failures

Examples:

# bad
def foo
  42
end

# good
def foo = 42

# bad
def calculate(x, y)
  x + y
end

# good
def calculate(x, y) = x + y

# bad (modifier-if with method call)
def clear!
  data_layer.clear! if data_layer.respond_to?(:clear!)
end

# good (uses traditional one-liner to avoid bugs)
def clear!() data_layer.clear! if data_layer.respond_to?(:clear!) end

What it skips:

• Methods already on a single line
• Methods with multiple statements
• Methods with heredocs
• Methods with rescue/ensure clauses
• Setter methods (ending with =)
• Methods with multi-statement blocks
• Methods with complex control flow (multi-line if/case)
• Methods where condensing would exceed line length

Tablecop sets opinionated defaults for RuboCop's built-in cops to achieve a table-like, condensed style. These are configured in config/default.yml and automatically applied when you use the plugin.

These cops are disabled because they conflict with Tablecop's alignment features:

# Conflicts with Tablecop/AlignAssignments
Layout/SpaceAroundOperators:
  Enabled: false  # Enforces exactly one space, undoes alignment

# Conflicts with Tablecop/SafeEndlessMethod
Style/SingleLineDoEndBlock:
  Enabled: false  # Would reformat SafeEndlessMethod output

Style/SingleLineMethods:
  Enabled: false  # Would reformat SafeEndlessMethod output

These cops have critical autocorrect bugs and are replaced by safer Tablecop equivalents:

# REPLACED by Tablecop/SafeEndlessMethod
Style/EndlessMethod:
  Enabled: false  # Destroys heredocs, orphans rescue clauses

Style/AmbiguousEndlessMethodDefinition:
  Enabled: false  # Related to EndlessMethod issues

# BUGS: Creates syntax errors and silent logic bugs
Style/DoubleNegation:
  Enabled: false  # !!false ≠ !false.nil?

Style/HashExcept:
  Enabled: false  # Breaks mixed symbol/string key handling

Layout/HashAlignment:
  EnforcedHashRocketStyle: table
  EnforcedColonStyle: table
  EnforcedLastArgumentHashStyle: always_inspect

Layout/ExtraSpacing:
  AllowForAlignment: true
  AllowBeforeTrailingComments: true
  ForceEqualSignAlignment: false  # Would cause infinite loops with heredocs

Layout/FirstArrayElementIndentation:
  EnforcedStyle: consistent  # Not aligned to brackets

Layout/FirstArgumentIndentation:
  EnforcedStyle: consistent  # Not aligned to parens

Layout/SpaceInsideHashLiteralBraces:
  EnforcedStyle: space  # { foo: 1 } not {foo: 1}

See config/default.yml for the complete configuration.

RuboCop has several autocorrect bugs that can destroy code. Tablecop's default configuration disables or works around these where possible. See docs/known-issues.md for detailed documentation of:

Here's what code looks like with Tablecop's formatting:

# Method alignment
class Calculator
  def add(x, y)      = x + y
  def subtract(x, y) = x - y
  def multiply(x, y) = x * y
  def divide(x, y)   = x / y
end

# Assignment alignment
class Config
  BASE_URL    = "https://example.com"
  API_VERSION = "v1"
  TIMEOUT     = 30

  def initialize
    @cache   = {}
    @enabled = true
    @retries = 3
  end
end

# Case statement condensing
def status_message(status)
  case status
  when :pending   then "Waiting for approval"
  when :approved  then "Ready to proceed"
  when :rejected  then "Cannot continue"
  when :completed then "All done"
  end
end

# Hash alignment
config = {
  host:     "localhost",
  port:     3000,
  ssl:      true,
  timeout:  30,
  retries:  3,
  pool:     10
}

Tablecop prioritizes:

1. Vertical alignment - Code aligned in columns is easier to scan
2. Density - Single-line expressions where appropriate reduce scrolling
3. Safety - Avoid RuboCop's known autocorrect bugs
4. Readability - Only condense when it improves clarity

This style works best for:

• Configuration files with many similar assignments
• Simple data transformations and mappings
• API clients with many similar methods
• DSLs with repetitive structures

This style may not work well for:

• Complex business logic with deep nesting
• Long method chains
• Files with highly variable line lengths

After checking out the repo, run bundle install to install dependencies. Then:

# Run RuboCop on the project
bundle exec rubocop

# Run autocorrect
bundle exec rubocop -a

Bug reports and pull requests are welcome on GitHub at https://github.com/v2-io/tablecop.

The gem is available as open source under the terms of the MIT License.