Add ameba (#15875)

Adds configuration and a CI job for https://github.com/crystal-ameba/ameba

I let ameba generate a config (`ameba --gen-config`) but replaced all exclusions with hard disables. Then I fixed the violations for some of the rules, which have already been merged in the last couple of days. So I removed the disables for these rules.

The configuration is annotated with explanations in code.

I have disabled most `Naming` and `Style` rules because most had large numbers of violations and some of them seem questionable. We can consider enabling some of the in the future, piece by piece

Author: straight-shoota

.ameba.yml

@@ -0,0 +1,194 @@
+# This configuration file was generated by `ameba --gen-config`
+# on 2025-06-02 13:57:07 UTC using Ameba version 1.7.0-dev.
+# The point is for the user to remove these configuration records
+# one by one as the reported problems are removed from the code base.
+#
+# For more details on any individual rule, run `ameba --only RuleName`.
+
+# Indicators for comment annotations:
+#
+# * `Disabled`: The rule is disabled because it does not seem useful for this repo (or in general).
+# * `BUG`: A bug in ameba prevents using this rule either entirely or for specific files.
+# * `FIXME`: The rule seems useful, but requires some effort to resolve. That's deferred for later.
+# * `TODO`: The rule might be useful, but we need to investigate whether we want to use it or not.
+
+Version: "1.7.0-dev"
+
+# Documentation
+# =========================
+
+# Disabled: What's the point in alerting about existing TODOs in code?
+Documentation/DocumentationAdmonition:
+  Enabled: false
+
+# Lint
+# =========================
+
+Lint/DebugCalls:
+  Excluded:
+  # Samples may legitimately use DebugCalls
+  - samples/**/*
+  # Explicit tests
+  - spec/std/pp_spec.cr
+
+Lint/DebuggerStatement:
+  Excluded:
+  # Explicit tests
+  - spec/debug/**/*
+
+# Disabled: `else nil` can be useful to explicitly show the consequence of the else branch
+Lint/ElseNil:
+  Enabled: false
+
+Lint/LiteralInCondition:
+  Excluded:
+  # Samples may legitimately use literals in conditions
+  - samples/**/*
+
+Lint/LiteralInInterpolation:
+  Excluded:
+  - spec/std/random_spec.cr # BUG: https://github.com/crystal-ameba/ameba/issues/611
+
+Lint/LiteralsComparison:
+  Excluded:
+  # Explicit tests for case equality on tuple literals
+  - spec/std/tuple_spec.cr
+
+# TODO: Investigate if some `not_nil!` calls can be avoided.
+Lint/NotNil:
+  Enabled: false
+
+Lint/RandZero:
+  Excluded:
+  # Explicit tests
+  - spec/std/random_spec.cr
+
+# FIXME: Resolve shadowing.
+Lint/ShadowingOuterLocalVar:
+  Enabled: false
+
+# TODO: Investigate file names and move to data directories.
+Lint/SpecFilename:
+  Enabled: false
+
+# BUG: https://github.com/crystal-ameba/ameba/issues/612
+Lint/TopLevelOperatorDefinition:
+  Enabled: false
+
+# Disabled: We have an explicit CI job for `typos`. No reason to run it through
+# ameba.
+Lint/Typos:
+  Enabled: false
+
+# TODO: Investigate unused arguments.
+Lint/UnusedArgument:
+  Enabled: false
+
+# TODO: Investigate unused block arguments.
+Lint/UnusedBlockArgument:
+  Enabled: false
+
+# FIXME: Investigate useless assigns.
+Lint/UselessAssign:
+  Enabled: false
+
+# Metrics
+# =========================
+
+# Disabled: Lot's of violations. Complexity is very individual.
+Metrics/CyclomaticComplexity:
+  Enabled: false
+
+# Naming
+# =========================
+# All disabled. There are many violations and some of the rules are questionable.
+# TODO: Consider enabling some of these rules.
+
+Naming/AccessorMethodName:
+  Enabled: false
+
+Naming/BinaryOperatorParameterName:
+  Enabled: false
+
+Naming/BlockParameterName:
+  Enabled: false
+
+# Disabled: All violations follow the spelling of identifiers in upstream
+# projects, e.g. for lib bindings.
+Naming/ConstantNames:
+  Enabled: false
+
+Naming/MethodNames:
+  Enabled: false
+
+Naming/PredicateName:
+  Enabled: false
+
+Naming/QueryBoolMethods:
+  Enabled: false
+
+Naming/RescuedExceptionsVariableName:
+  Enabled: false
+
+Naming/TypeNames:
+  Enabled: false
+
+Naming/VariableNames:
+  Enabled: false
+
+# Performance
+# =========================
+
+Performance/AnyInsteadOfEmpty:
+  Excluded:
+  # These specs explicitly test `#any?` implementations
+  - spec/std/bit_array_spec.cr
+  - spec/std/enumerable_spec.cr
+  - spec/std/hash_spec.cr
+
+# Style
+# =========================
+# All disabled. There are many violations and some of the rules are questionable.
+# TODO: Consider enabling some of these rules.
+
+Style/HeredocEscape:
+  Enabled: false
+
+Style/HeredocIndent:
+  Enabled: false
+
+Style/MultilineCurlyBlock:
+  Enabled: false
+
+# Disabled: This rule seems too strict when any negation inside a complex condition is
+# considered a violation. https://github.com/crystal-ameba/ameba/issues/621
+Style/NegatedConditionsInUnless:
+  Enabled: false
+
+# BUG: https://github.com/crystal-ameba/ameba/issues/614
+Style/ParenthesesAroundCondition:
+  Enabled: false
+
+Style/PercentLiteralDelimiters:
+  Enabled: false
+
+Style/RedundantBegin:
+  Enabled: false
+
+Style/RedundantNext:
+  Enabled: false
+
+Style/RedundantReturn:
+  Enabled: false
+
+Style/RedundantSelf:
+  Enabled: false
+
+Style/UnlessElse:
+  Enabled: false
+
+Style/VerboseBlock:
+  Enabled: false
+
+Style/WhileTrue:
+  Enabled: false

.github/workflows/linux.yml

@@ -113,3 +113,12 @@ jobs:
       uses: crate-ci/[email protected]
       env:
         CLICOLOR: 1
+
+  lint_ameba:
+    runs-on: ubuntu-latest
+    container: ghcr.io/crystal-ameba/ameba:sha-d861f4ed0f904e0ecdad11c26f98e968f7d95afa # 1.7.0-dev
+    steps:
+      - name: Download Crystal source
+        uses: actions/checkout@v4
+
+      - run: ameba

scripts/generate_windows_zone_names.cr

@@ -45,7 +45,7 @@ windows_zone_names_items = entries.compact_map do |tzdata_name, territory, windo
 
   {windows_name, zone1.name, zone2.name, location.name}
 rescue err : Time::Location::InvalidLocationNameError
-  pp err
+  puts err
   nil
 end
 

spec/llvm-ir/pass-closure-to-c-debug-loc.cr

@@ -3,7 +3,7 @@ lib Foo
 end
 
 def raise(msg)
-  while true
+  while true # ameba:disable Lint/EmptyLoop
   end
 end
 

spec/std/iterator_spec.cr

@@ -663,7 +663,7 @@ describe Iterator do
 
   describe "uniq" do
     it "without block" do
-      iter = (1..8).each.map { |x| x % 3 }.uniq
+      iter = (1..8).each.map { |x| x % 3 }.uniq # ameba:disable Performance/ChainedCallWithNoBang
       iter.next.should eq(1)
       iter.next.should eq(2)
       iter.next.should eq(0)
@@ -806,7 +806,7 @@ describe Iterator do
     end
 
     it "flattens nested struct iterators with internal state being value types" do
-      iter = (1..2).each.map { |i| StructIter.new(10 * i + 1, 10 * i + 3) }.flatten
+      iter = (1..2).each.map { |i| StructIter.new(10 * i + 1, 10 * i + 3) }.flatten # ameba:disable Performance/FlattenAfterMap
 
       iter.next.should eq(11)
       iter.next.should eq(12)

src/kernel.cr

@@ -468,7 +468,7 @@ end
 # See also: `Object#inspect(io)`.
 def p(*objects)
   objects.each do |obj|
-    p obj
+    p obj # ameba:disable Lint/DebugCalls
   end
   objects
 end
@@ -482,7 +482,7 @@ end
 #
 # See `Object#inspect(io)`
 def p(**objects)
-  p(objects) unless objects.empty?
+  p(objects) unless objects.empty? # ameba:disable Lint/DebugCalls
 end
 
 # Pretty prints *object* to `STDOUT` followed
@@ -501,7 +501,7 @@ end
 # See also: `Object#pretty_print(pp)`.
 def pp(*objects)
   objects.each do |obj|
-    pp obj
+    pp obj # ameba:disable Lint/DebugCalls
   end
   objects
 end
@@ -515,7 +515,7 @@ end
 #
 # See `Object#pretty_print(pp)`
 def pp(**objects)
-  pp(objects) unless objects.empty?
+  pp(objects) unless objects.empty? # ameba:disable Lint/DebugCalls
 end
 
 # Registers the given `Proc` for execution when the program exits regularly.