From 726a5c9f59f9c499a56ea58ede8db13f88e6fe62 Mon Sep 17 00:00:00 2001
From: Marc-Andre Lafortune <github@marc-andre.ca>
Date: Thu, 11 Jun 2020 12:31:10 -0400
Subject: [PATCH] NodePattern: Use `param === node` to match params.

---
 docs/modules/ROOT/pages/node_pattern.adoc | 35 +++++++++++++++++++++++
 lib/rubocop/ast/node_pattern.rb           |  5 ++--
 spec/rubocop/ast/node_pattern_spec.rb     | 10 +++++++
 3 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/docs/modules/ROOT/pages/node_pattern.adoc b/docs/modules/ROOT/pages/node_pattern.adoc
index 6aa8cfe19..1b238298e 100644
--- a/docs/modules/ROOT/pages/node_pattern.adoc
+++ b/docs/modules/ROOT/pages/node_pattern.adoc
@@ -374,6 +374,41 @@ def_node_matcher :initializing_with_user?, <<~PATTERN
 PATTERN
 ----
 
+== `%` for arguments
+
+Arguments can be passed to matchers, either as external method arguments,
+or to be used to compare elements. An example of method argument:
+
+[source,ruby]
+----
+def multiple_of?(n, factor)
+  n % factor == 0
+end
+
+def_node_matcher :int_node_multiple?, '(int #multiple_of?(%1))'
+
+# ...
+
+int_node_multiple?(node, 10) # => true if node is an 'int' node with a multiple of 10
+----
+
+Arguments can be used to match nodes directly:
+
+[source,ruby]
+----
+def_node_matcher :has_sensitive_data?, '(hash <(pair %1 $_)>...)'
+
+# ...
+
+has_user_data?(node, :password) # => true if node is a hash with a key +:password+
+
+# matching uses ===, so to match strings or symbols, 'pass' or 'password' one can:
+has_user_data?(node, /^pass(word)?$/i)
+
+# one can also pass lambdas...
+has_user_data?(node, ->(key) { # return true or false depending on key })
+----
+
 == `nil` or `nil?`
 
 Take a special attention to nil behavior:
diff --git a/lib/rubocop/ast/node_pattern.rb b/lib/rubocop/ast/node_pattern.rb
index eef631934..e3bc4bbbe 100644
--- a/lib/rubocop/ast/node_pattern.rb
+++ b/lib/rubocop/ast/node_pattern.rb
@@ -70,7 +70,8 @@ module AST
     #     '(send %1 _)'       # % stands for a parameter which must be supplied to
     #                         # #match at matching time
     #                         # it will be compared to the corresponding value in
-    #                         # the AST using #==
+    #                         # the AST using #=== so you can pass Procs, Regexp
+    #                         # in addition to Nodes or literals.
     #                         # a bare '%' is the same as '%1'
     #                         # the number of extra parameters passed to #match
     #                         # must equal the highest % value in the pattern
@@ -612,7 +613,7 @@ def compile_nodetype(type)
         end
 
         def compile_param(number)
-          "#{CUR_ELEMENT} == #{get_param(number)}"
+          "#{get_param(number)} === #{CUR_ELEMENT}"
         end
 
         def compile_args(tokens)
diff --git a/spec/rubocop/ast/node_pattern_spec.rb b/spec/rubocop/ast/node_pattern_spec.rb
index 7ccfae628..790d9498c 100644
--- a/spec/rubocop/ast/node_pattern_spec.rb
+++ b/spec/rubocop/ast/node_pattern_spec.rb
@@ -1146,6 +1146,16 @@
       let(:ruby) { '10' }
 
       it_behaves_like 'matching'
+
+      context 'in root position' do
+        let(:pattern) { '%1' }
+        let(:matcher) { Object.new }
+        let(:params) { [matcher] }
+        let(:ruby) { '10' }
+        before { expect(matcher).to receive(:===).with(s(:int, 10)).and_return true }
+
+        it_behaves_like 'matching'
+      end
     end
 
     context 'in a nested sequence' do