Add Performance/MinMaxAfterMap rule

spec/ameba/rule/performance/minmax_after_map_spec.cr

@@ -0,0 +1,45 @@
+require "../../../spec_helper"
+
+module Ameba::Rule::Performance
+  subject = MinMaxAfterMap.new
+
+  describe MinMaxAfterMap do
+    it "passes if there is no potential performance improvements" do
+      expect_no_issues subject, <<-CRYSTAL
+        %w[Alice Bob].map { |name| name.size }.min(2)
+        %w[Alice Bob].map { |name| name.size }.max(2)
+        CRYSTAL
+    end
+
+    it "reports if there is a `min/max/minmax` call followed by `map`" do
+      source = expect_issue subject, <<-CRYSTAL
+        %w[Alice Bob].map { |name| name.size }.min
+                    # ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: Use `min_of {...}` instead of `map {...}.min`.
+        %w[Alice Bob].map(&.size).max.zero?
+                    # ^^^^^^^^^^^^^^^ error: Use `max_of {...}` instead of `map {...}.max`.
+        %w[Alice Bob].map(&.size).minmax?
+                    # ^^^^^^^^^^^^^^^^^^^ error: Use `minmax_of? {...}` instead of `map {...}.minmax?`.
+        CRYSTAL
+
+      expect_correction source, <<-CRYSTAL
+        %w[Alice Bob].min_of { |name| name.size }
+        %w[Alice Bob].max_of(&.size).zero?
+        %w[Alice Bob].minmax_of?(&.size)
+        CRYSTAL
+    end
+
+    it "does not report if source is a spec" do
+      expect_no_issues subject, path: "source_spec.cr", code: <<-CRYSTAL
+        %w[Alice Bob].map(&.size).min
+        CRYSTAL
+    end
+
+    context "macro" do
+      it "doesn't report in macro scope" do
+        expect_no_issues subject, <<-CRYSTAL
+          {{ %w[Alice Bob].map(&.size).min }}
+          CRYSTAL
+      end
+    end
+  end
+end