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Variable scope & useless assignments (#41)

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* AST::Visitor -> AST::NodeVisitor

* Scope & ScopeVisitor

* Useless assignment rule

* Instance vars and useless assignments

* Multiple assigns one by one

* Support outer scope

* Variable used in the useless assignment

* Support OpAssign & MultiAssign

* Captured by block

* Variable, Assignment, Reference & Refactoring

* Variable has references, Assignment can be referenced

* Branch entity

* Handle useless assignments in branches

* Handle assignments in a loop

* Handle branch equality

* Handle special var `$?` assignment

* Improve captured by block stuff

* Avoid assignments in property definitions

(UselessAssign rule reports an warning)

* Support MacroIf and MacroFor branches

* Handle assignments with shadowed vars in inner scopes

* Add method arguments as scope variables

* Handle case if branch is blank

* Top level scope

* Handle case when branch is nop?
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2
spec/ameba/rule/unneded_disable_directive_spec.cr
View file

@ -35,7 +35,7 @@ module Ameba::Rule
subject.catch(s).should be_valid
end
it "failes if there is unneeded directive" do
it "fails if there is unneeded directive" do
s = Source.new %Q(
# ameba:disable #{NamedRule.name}
a = 1

813
spec/ameba/rule/useless_assign_spec.cr Normal file
View file

@ -0,0 +1,813 @@
require "../../spec_helper"
module Ameba::Rule
describe UselessAssign do
subject = UselessAssign.new
it "does not report used assigments" do
s = Source.new %(
def method
a = 2
a
end
)
subject.catch(s).should be_valid
end
it "reports a useless assignment in a method" do
s = Source.new %(
def method
a = 2
end
)
subject.catch(s).should_not be_valid
end
it "reports a useless assignment in a proc" do
s = Source.new %(
->() {
a = 2
}
)
subject.catch(s).should_not be_valid
end
it "reports a useless assignment in a block" do
s = Source.new %(
def method
3.times do
a = 1
end
end
)
subject.catch(s).should_not be_valid
end
it "reports a useless assignment in a proc inside def" do
s = Source.new %(
def method
->() {
a = 2
}
end
)
subject.catch(s).should_not be_valid
end
it "reports a useless assignment in a proc inside a block" do
s = Source.new %(
def method
3.times do
->() {
a = 2
}
end
end
)
subject.catch(s).should_not be_valid
end
it "reports rule, position and a message" do
s = Source.new %(
def method
a = 2
end
), "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:3:11"
error.message.should eq "Useless assignment to variable `a`"
end
it "does not report useless assignment of instance var" do
s = Source.new %(
class Cls
def initialize(@name)
end
end
)
subject.catch(s).should be_valid
end
it "does not report if assignment used in the inner block scope" do
s = Source.new %(
def method
var = true
3.times { var = false }
end
)
subject.catch(s).should be_valid
end
it "reports if assigned is not referenced in the inner block scope" do
s = Source.new %(
def method
var = true
3.times {}
end
)
subject.catch(s).should_not be_valid
end
it "doesn't report if assignment in referenced in inner block" do
s = Source.new %(
def method
two = true
3.times do
mutex.synchronize do
two = 2
end
end
two.should be_true
end
)
subject.catch(s).should be_valid
end
it "reports if first assignment is useless" do
s = Source.new %(
def method
var = true
var = false
var
end
)
subject.catch(s).should_not be_valid
s.errors.first.location.to_s.should eq ":3:11"
end
it "reports if variable reassigned and not used" do
s = Source.new %(
def method
var = true
var = false
end
)
subject.catch(s).should_not be_valid
end
it "does not report if variable used in a condition" do
s = Source.new %(
def method
a = 1
if a
nil
end
end
)
subject.catch(s).should be_valid
end
it "reports second assignment as useless" do
s = Source.new %(
def method
a = 1
a = a + 1
end
)
subject.catch(s).should_not be_valid
end
it "does not report if variable is referenced in other assignment" do
s = Source.new %(
def method
if f = get_something
@f = f
end
end
)
subject.catch(s).should be_valid
end
it "does not report if variable is referenced in a setter" do
s = Source.new %(
def method
foo = 2
table[foo] ||= "bar"
end
)
subject.catch(s).should be_valid
end
it "does not report if variable is reassigned but not referenced" do
s = Source.new %(
def method
foo = 1
puts foo
foo = 2
end
)
subject.catch(s).should_not be_valid
end
it "does not report if variable is referenced in a call" do
s = Source.new %(
def method
if f = FORMATTER
@formatter = f.new
end
end
)
subject.catch(s).should be_valid
end
it "does not report if a setter is invoked with operator assignment" do
s = Source.new %(
def method
obj = {} of Symbol => Int32
obj[:name] = 3
end
)
subject.catch(s).should be_valid
end
it "does not report if global var" do
s = Source.new %(
def method
$? = 3
end
)
subject.catch(s).should be_valid
end
it "does not report if assignment is referenced in a proc" do
s = Source.new %(
def method
called = false
->() { called = true }
called
end
)
subject.catch(s).should be_valid
end
it "reports if variable is shadowed in inner scope" do
s = Source.new %(
def method
i = 1
3.times do |i|
i + 1
end
end
)
subject.catch(s).should_not be_valid
end
it "does not report if parameter is referenced after the branch" do
s = Source.new %(
def method(param)
3.times do
param = 3
end
param
end
)
subject.catch(s).should be_valid
end
context "op assigns" do
it "does not report if variable is referenced below the op assign" do
s = Source.new %(
def method
a = 1
a += 1
a
end
)
subject.catch(s).should be_valid
end
it "does not report if variable is referenced in op assign few times" do
s = Source.new %(
def method
a = 1
a += 1
a += 1
a = a + 1
a
end
)
subject.catch(s).should be_valid
end
it "reports if variable is not referenced below the op assign" do
s = Source.new %(
def method
a = 1
a += 1
end
)
subject.catch(s).should_not be_valid
end
it "reports rule, location and a message" do
s = Source.new %(
def method
b = 2
a = 3
a += 1
end
), "source.cr"
subject.catch(s).should_not be_valid
error = s.errors.last
error.rule.should_not be_nil
error.location.to_s.should eq "source.cr:5:13"
error.message.should eq "Useless assignment to variable `a`"
end
end
context "multi assigns" do
it "does not report if all assigns are referenced" do
s = Source.new %(
def method
a, b = {1, 2}
a + b
end
)
subject.catch(s).should be_valid
end
it "reports if one assign is not referenced" do
s = Source.new %(
def method
a, b = {1, 2}
a
end
)
subject.catch(s).should_not be_valid
error = s.errors.first
error.location.to_s.should eq ":3:16"
error.message.should eq "Useless assignment to variable `b`"
end
it "reports if both assigns are reassigned and useless" do
s = Source.new %(
def method
a, b = {1, 2}
a, b = {3, 4}
end
)
subject.catch(s).should_not be_valid
end
it "reports if both assigns are not referenced" do
s = Source.new %(
def method
a, b = {1, 2}
end
)
subject.catch(s).should_not be_valid
error = s.errors.first
error.location.to_s.should eq ":3:13"
error.message.should eq "Useless assignment to variable `a`"
error = s.errors.last
error.location.to_s.should eq ":3:16"
error.message.should eq "Useless assignment to variable `b`"
end
end
context "top level" do
it "reports if assignment is not referenced" do
s = Source.new %(
a = 1
a = 2
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 2
s.errors.first.location.to_s.should eq ":2:11"
s.errors.last.location.to_s.should eq ":3:11"
end
it "doesn't report if assignments are referenced" do
s = Source.new %(
a = 1
a += 1
a
b, c = {1, 2}
b
c
)
subject.catch(s).should be_valid
end
it "doesn't report if assignment is captured by block" do
s = Source.new %(
a = 1
3.times do
a = 2
end
)
subject.catch(s).should be_valid
end
end
context "branching" do
context "if-then-else" do
it "doesn't report if assignment is consumed by branches" do
s = Source.new %(
def method
a = 0
if something
a = 1
else
a = 2
end
a
end
)
subject.catch(s).should be_valid
end
it "doesn't report if assignment is in one branch" do
s = Source.new %(
def method
a = 0
if something
a = 1
else
nil
end
a
end
)
subject.catch(s).should be_valid
end
it "doesn't report if assignment is in one line branch" do
s = Source.new %(
def method
a = 0
a = 1 if something
a
end
)
subject.catch(s).should be_valid
end
it "reports if assignment is useless in the branch" do
s = Source.new %(
def method(a)
if a
a = 2
end
end
)
subject.catch(s).should_not be_valid
end
it "reports if only last assignment is referenced in a branch" do
s = Source.new %(
def method(a)
a = 1
if a
a = 2
a = 3
end
a
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 1
s.errors.first.location.to_s.should eq ":5:17"
end
it "does not report of assignments are referenced in all branches" do
s = Source.new %(
def method
if matches
matches = owner.lookup_matches signature
else
matches = owner.lookup_matches signature
end
matches
end
)
subject.catch(s).should be_valid
end
it "does not report referenced assignments in inner branches" do
s = Source.new %(
def method
has_newline = false
if something
do_something unless false
has_newline = false
else
do_something if true
has_newline = true
end
has_newline
end
)
subject.catch(s).should be_valid
end
end
context "unless-then-else" do
it "doesn't report if assignment is consumed by branches" do
s = Source.new %(
def method
a = 0
unless something
a = 1
else
a = 2
end
a
end
)
subject.catch(s).should be_valid
end
it "reports if there is a useless assignment in a branch" do
s = Source.new %(
def method
a = 0
unless something
a = 1
a = 2
else
a = 2
end
a
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 1
s.errors.first.location.to_s.should eq ":5:17"
end
end
context "case" do
it "does not report if assignment is referenced" do
s = Source.new %(
def method(a)
case a
when /foo/
a = 1
when /bar/
a = 2
end
puts a
end
)
subject.catch(s).should be_valid
end
it "reports if assignment is useless" do
s = Source.new %(
def method(a)
case a
when /foo/
a = 1
when /bar/
a = 2
end
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 2
s.errors.first.location.to_s.should eq ":5:17"
s.errors.last.location.to_s.should eq ":7:17"
end
end
context "binary operator" do
it "does not report if assignment is referenced" do
s = Source.new %(
def method(a)
(a = 1) && (b = 1)
a + b
end
)
subject.catch(s).should be_valid
end
it "reports if assignment is useless" do
s = Source.new %(
def method(a)
(a = 1) || (b = 1)
a
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 1
s.errors.first.location.to_s.should eq ":3:27"
end
end
context "while" do
it "does not report if assignment is referenced" do
s = Source.new %(
def method(a)
while a < 10
a = a + 1
end
a
end
)
subject.catch(s).should be_valid
end
it "reports if assignment is useless" do
s = Source.new %(
def method(a)
while a < 10
b = a
end
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 1
s.errors.first.location.to_s.should eq ":4:17"
end
it "does not report if assignment is referenced in a loop" do
s = Source.new %(
def method
a = 3
result = 0
while result < 10
result += a
a = a + 1
end
result
end
)
subject.catch(s).should be_valid
end
it "does not report if assignment is referenced as param in a loop" do
s = Source.new %(
def method(a)
result = 0
while result < 10
result += a
a = a + 1
end
result
end
)
subject.catch(s).should be_valid
end
it "does not report if assignment is referenced in loop and inner branch" do
s = Source.new %(
def method(a)
result = 0
while result < 10
result += a
if result > 0
a = a + 1
else
a = 3
end
end
result
end
)
subject.catch(s).should be_valid
end
it "works properly if there is branch with blank node" do
s = Source.new %(
def visit
count = 0
while true
break if count == 1
case something
when :any
else
:anything_else
end
count += 1
end
end
)
subject.catch(s).should be_valid
end
end
context "until" do
it "does not report if assignment is referenced" do
s = Source.new %(
def method(a)
until a > 10
a = a + 1
end
a
end
)
subject.catch(s).should be_valid
end
it "reports if assignment is useless" do
s = Source.new %(
def method(a)
until a > 10
b = a + 1
end
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 1
s.errors.first.location.to_s.should eq ":4:17"
end
end
context "exception handler" do
it "does not report if assignment is referenced in body" do
s = Source.new %(
def method(a)
a = 2
rescue
a
end
)
subject.catch(s).should be_valid
end
it "doesn't report if assignment is referenced in ensure" do
s = Source.new %(
def method(a)
a = 2
ensure
a
end
)
subject.catch(s).should be_valid
end
it "doesn't report if assignment is referenced in else" do
s = Source.new %(
def method(a)
a = 2
rescue
else
a
end
)
subject.catch(s).should be_valid
end
it "reports if assignment is useless" do
s = Source.new %(
def method(a)
rescue
a = 2
end
)
subject.catch(s).should_not be_valid
s.errors.size.should eq 1
s.errors.first.location.to_s.should eq ":4:15"
end
end
end
context "macro" do
it "doesn't report if assignment is referenced in macro" do
s = Source.new %(
def method
a = 2
{% if flag?(:bits64) %}
a.to_s
{% else %}
a
{% end %}
end
)
subject.catch(s).should be_valid
end
it "doesn't report referenced assignments in macro literal" do
s = Source.new %(
def method
a = 2
{% if flag?(:bits64) %}
a = 3
{% else %}
a = 4
{% end %}
puts a
end
)
subject.catch(s).should be_valid
end
end
end
end