New rule: rand zero

This commit is contained in:
Vitalii Elenhaupt 2018-03-08 18:55:35 +02:00 committed by V. Elenhaupt
parent 672de9f86b
commit 2f837375ec
2 changed files with 82 additions and 0 deletions

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require "../../spec_helper"
module Ameba::Rule
describe RandZero do
subject = RandZero.new
it "passes if it is not rand(1) or rand(0)" do
s = Source.new %(
rand(1.0)
rand(0.11)
rand(2)
)
subject.catch(s).should be_valid
end
it "fails if it is rand(0)" do
s = Source.new "rand(0)"
subject.catch(s).should_not be_valid
end
it "fails if it is rand(1)" do
s = Source.new "rand(1)"
subject.catch(s).should_not be_valid
end
it "reports rule, location and a message" do
s = Source.new "rand(1)", "source.cr"
subject.catch(s).should_not be_valid
error = s.errors.first
error.rule.should_not be_nil
error.location.to_s.should eq "source.cr:1:1"
error.message.should eq "rand(1) always returns 0"
end
end
end

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module Ameba::Rule
# A rule that disallows `rand(0)` and `rand(1)` calls.
# Such calls always return `0`.
#
# For example:
#
# ```
# rand(1)
# ```
#
# Should be written as:
#
# ```
# rand
# # or
# rand(2)
# ```
#
# YAML configuration example:
#
# ```
# RandZero:
# Enabled: true
# ```
#
struct RandZero < Base
properties do
description = "Disallows rand zero calls"
end
def test(source)
AST::Visitor.new self, source
end
def test(source, node : Crystal::Call)
return unless node.name == "rand" &&
node.args.size == 1 &&
(arg = node.args.first) &&
(arg.is_a? Crystal::NumberLiteral) &&
(value = arg.value) &&
(value == "0" || value == "1")
source.error self, node.location, "#{node} always returns 0"
end
end
end