Ameba v1.0.0 has been released

This release includes a long-waiting autocorrection feature, new rules and several improvements. Checkout the release notes to see a full scope of changes.

Crystal compatibility

This release introduces Crystal 1.4 compatibility and breaks compatibility of previous Crystal versions. Use the latest Ameba bugfix release 0.14.4 if you need a compatibility of Crystal 1.3.x or below.

Autocorrection

Thanks to community, there is a huge step forward implementing autocorrection for Ameba. The feature was originally developed in #248 and afterwards improved in a several cycles.

Now if Ameba reports an issue which can be corrected, it adds a [Correctable] notice:

$ ameba --only Style/RedundantBegin src/file_utils.cr

src/file_utils.cr:428:5 [Correctable]
[C] Style/RedundantBegin: Redundant `begin` block detected
> begin
  ^---^

meaning, if you append a new --fix command-line flag to the command it will automatically correct the issue adding another notice [Corrected]:

ameba --only Style/RedundantBegin src/file_utils.cr --fix

src/file_utils.cr:428:5 [Corrected]
[C] Style/RedundantBegin: Redundant `begin` block detected
> begin
  ^---^

using a git diff we can quickly check that Ameba removed a reported redundant begin block and used the exception handler as part of a method:

diff --git a/src/file_utils.cr b/src/file_utils.cr
index e82e3c1e1..d416ed05b 100644
--- a/src/file_utils.cr
+++ b/src/file_utils.cr
@@ -425,10 +425,8 @@ module FileUtils
   # FileUtils.rm_rf("non_existent_file")
   # ```
   def rm_rf(path : Path | String) : Nil
-    begin
-      rm_r(path)
-    rescue File::Error
-    end
+    rm_r(path)
+  rescue File::Error
   end

Note: not all rules support autocorrection yet, but if you see a [Correctable] flag on a reported issue, do not hesitate to autocorrect it in order to save some time during refactoring.

New rules

Lint/AmbiguousAssignment

A tiny rule that checks for mistyped shorthand assignments.

Bad

x =- y
x =+ y
x =! y

Good

x -= y # or x = -y
x += y # or x = +y
x != y # or x = !y

Lint/DebugCalls

A rule that disallows calls to debug-related methods. This is because we don’t want debug calls accidentally being committed into our codebase.

a = 2
pp! a # error: Possibly forgotten debug-related `pp!` call detected
a = a + 1

Checkout the API doc to see a full list of supported debug-related calls.

Style/GuardClause

A rule that enforces a guard clause instead of wrapping the code inside a conditional expression.

Bad

def test
  if something
    work
  end
end

Good

def test
  return unless something

  work
end

New spec matchers

Ameba has a high code coverage which was obviously achieved by a big amount of tests. However, most of the rule specs were too imperative and it led to code duplication and some readability issues.

In this release were introduced a new spec matchers for rule tests. This new declarative approach allows to easily track all the reported issues in specs.

it "reports multiple shared variables in spawn" do
  expect_issue subject, %(
    foo, bar, baz = 0, 0, 0

    while foo < 10
      baz += 1

      spawn do
        puts foo
            # ^^^ error: Shared variable `foo` is used in fiber
        puts foo + bar + baz
            # ^^^ error: Shared variable `foo` is used in fiber
                        # ^^^ error: Shared variable `baz` is used in fiber
      end

      foo += 1
    end
  )
end

Some explanation:

• ^^^ - tracks location of the reported node
• error - severity of the issue
• Shared variable 'foo' is used in fiber - the reported error message

These new matchers are used internally and of course can be used by Ameba extensions. Checkout the doc for more details.