class

Ameba::Rule::Lint::UnusedExpression

Inherits YAML::Serializable < Ameba::Rule::Base < Ameba::Config::RuleConfig < Reference < Object

A rule that disallows unused expressions.

For example, this is considered invalid:

a = obj.method do |x|
  x == 1 # => Comparison operation has no effect
  puts x
end

Float64 | StaticArray(Float64, 10)

pointerof(foo)

And these are considered valid:

a = obj.method do |x|
  x == 1
end

foo : Float64 | StaticArray(Float64, 10) = 0.1

bar = pointerof(foo)

This rule currently supports checking for unused:

comparison operators: <, >=, etc.
generics and unions: String?, Int32 | Float64, etc.
literals: strings, bools, chars, hashes, arrays, range, etc.
pseudo-method calls: sizeof, is_a? etc.
variable access: local, @ivar, @@cvar and self

YAML configuration example:

Lint/UnusedExpression:
  Enabled: true

Constants

COMPARISON_OPERATORS = ["==", "!=", "<", "<=", ">", ">=", "<=>"] of ::String

MSG_CLASS_VAR = "Class variable access is unused"

MSG_COMPARISON = "Comparison operation is unused"

MSG_GENERIC = "Generic type is unused"

MSG_INSTANCE_VAR = "Instance variable access is unused"

MSG_LITERAL = "Literal value is unused"

MSG_LOCAL_VAR = "Local variable access is unused"

MSG_PSEUDO_METHOD = "Pseudo-method call is unused"

MSG_SELF = "`self` access is unused"

MSG_UNION = "Union type is unused"

Constructors

new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)

new(config = nil)

A rule that disallows unused expressions.

For example, this is considered invalid:

a = obj.method do |x|
  x == 1 # => Comparison operation has no effect
  puts x
end

Float64 | StaticArray(Float64, 10)

pointerof(foo)

And these are considered valid:

a = obj.method do |x|
  x == 1
end

foo : Float64 | StaticArray(Float64, 10) = 0.1

bar = pointerof(foo)

This rule currently supports checking for unused:

comparison operators: <, >=, etc.
generics and unions: String?, Int32 | Float64, etc.
literals: strings, bools, chars, hashes, arrays, range, etc.
pseudo-method calls: sizeof, is_a? etc.
variable access: local, @ivar, @@cvar and self

YAML configuration example:

Lint/UnusedExpression:
  Enabled: true

Source

new(*, __context_for_yaml_serializable ctx : YAML::ParseContext, __node_for_yaml_serializable node : YAML::Nodes::Node)

Class methods

deprecated?

Returns true if this rule is deprecated, false otherwise.

deprecation_reason

Returns the deprecation reason for this rule, if there is any.

documentation_url

Returns the documentation URL for this rule.

Ameba::Rule::Lint::Syntax.documentation_url
# => "https://crystal-ameba.org/api/master/Ameba/Rule/Lint/Syntax.html"

parsed_doc

Returns the documentation for this rule, if there is any.

module Ameba
  # This is a test rule.
  # Does nothing.
  class Rule::MyRule < Rule::Base
    def test(source)
    end
  end
end

Ameba::Rule::MyRule.parsed_doc # => "This is a test rule.\nDoes nothing."

to_json_schema(builder : JSON::Builder) : Nil

Source

Instance methods

description

description=(description : String)

enabled=(enabled : Bool)

enabled?

excluded

excluded=(excluded : Set(String) | Nil)

severity

severity=(severity : Ameba::Severity)

since_version

Source

since_version=(since_version : String)

test(source, node : Crystal::ClassVar, in_macro : Bool)

Source

test(source, node : Crystal::Call, in_macro : Bool)

Source

test(source, node : Crystal::Generic, in_macro : Bool)

Source

test(source, node : Crystal::InstanceVar, in_macro : Bool)

Source

test(source, node : Crystal::RegexLiteral, in_macro : Bool)

Source

Source

test(source, node : Crystal::Var, in_macro : Bool)

Source

Source

test(source : Source)

This method is designed to test the source passed in. If source has issues that are tested by this rule, it should add an issue.

By default it uses a node visitor to traverse all the nodes in the source.

NOTE: Must be overridden for other type of rules.

Source