New rule: comparison to boolean

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Vitalii Elenhaupt 2017-10-31 23:15:24 +02:00
parent 11005930f6
commit 6d9f1c67ed
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3 changed files with 140 additions and 0 deletions

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require "../../spec_helper"
module Ameba::Rules
subject = ComparisonToBoolean.new
describe ComparisonToBoolean do
it "passes if there is no comparison to boolean" do
source = Source.new %(
a = true
if a
:ok
end
if true
:ok
end
unless s.empty?
:ok
end
:ok if a
:ok if a != 1
:ok if a == "true"
case a
when true
:ok
when false
:not_ok
end
)
subject.catch(source).valid?.should be_true
end
context "boolean on the right" do
it "fails if there is == comparison to boolean" do
source = Source.new %(
if s.empty? == true
:ok
end
)
subject.catch(source).valid?.should be_false
end
it "fails if there is != comparison to boolean" do
source = Source.new %(
if a != false
:ok
end
)
subject.catch(source).valid?.should be_false
end
it "fails if there is case comparison to boolean" do
source = Source.new %(
a === true
)
subject.catch(source).valid?.should be_false
end
it "reports rule, pos and message" do
source = Source.new "a != true"
subject.catch(source)
error = source.errors.first
error.rule.should_not be_nil
error.pos.should eq 1
error.message.should eq "Comparison to a boolean is pointless"
end
end
context "boolean on the left" do
it "fails if there is == comparison to boolean" do
source = Source.new %(
if true == s.empty?
:ok
end
)
subject.catch(source).valid?.should be_false
end
it "fails if there is != comparison to boolean" do
source = Source.new %(
if false != a
:ok
end
)
subject.catch(source).valid?.should be_false
end
it "fails if there is case comparison to boolean" do
source = Source.new %(
true === a
)
subject.catch(source).valid?.should be_false
end
it "reports rule, pos and message" do
source = Source.new "true != a"
subject.catch(source)
error = source.errors.first
error.rule.should_not be_nil
error.pos.should eq 1
error.message.should eq "Comparison to a boolean is pointless"
end
end
end
end

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module Ameba
RULES = [
Rules::ComparisonToBoolean,
Rules::LineLength,
Rules::TrailingBlankLines,
Rules::TrailingWhitespace,

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# A rule that disallows comparison to booleans.
#
# For example, these are considered invalid:
#
# ```crystal
# foo == true
# bar != false
# false === baz
# ```
# This is because these expressions evaluate to `true` or `false`, so you
# could get the same result by using either the variable directly, or negating
# the variable.
Ameba.rule ComparisonToBoolean do |source|
ComparisonToBooleanVisitor.new self, source
end
Ameba.visitor ComparisonToBoolean, Crystal::Call do |node|
if %w(== != ===).includes?(node.name) && (
node.args.first?.try &.is_a?(Crystal::BoolLiteral) ||
node.obj.is_a?(Crystal::BoolLiteral)
)
@source.error @rule, node.location.try &.line_number,
"Comparison to a boolean is pointless"
end
end