Adds thread-safe PaperTrail.whodunnit(value) { ... }

Allows to set whodunnit for the block, e.g.

PaperTrail.whodunnit("me") { Booking.past.not_charged.each(&:charge) }

CHANGELOG.md

@@ -11,7 +11,8 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Added
 
-- None
+- [#932](https://github.com/airblade/paper_trail/pull/932) -
+  `PaperTrail.whodunnit` now accepts a block.
 
 ### Fixed
 

README.md

@@ -708,6 +708,14 @@ widget.update_attributes :name => 'Wibble'
 widget.versions.last.whodunnit              # Andy Stewart
 ```
 
+`whodunnit` also accepts a block, a convenient way to temporarily set the value.
+
+```ruby
+PaperTrail.whodunnit("Dorian Marié") do
+  widget.update_attributes :name => 'Wibble'
+end
+```
+
 If your controller has a `current_user` method, PaperTrail provides a
 `before_action` that will assign `current_user.id` to `PaperTrail.whodunnit`.
 You can add this `before_action` to your `ApplicationController`.

lib/paper_trail.rb

@@ -87,10 +87,33 @@ module PaperTrail
       paper_trail_store[:whodunnit] = value
     end
 
-    # Returns who is reponsible for any changes that occur.
+    # If nothing passed, returns who is reponsible for any changes that occur.
+    #
+    #   PaperTrail.whodunnit = "someone"
+    #   PaperTrail.whodunnit # => "someone"
+    #
+    # If value and block passed, set this value as whodunnit for the duration of the block
+    #
+    #   PaperTrail.whodunnit("me") do
+    #     puts PaperTrail.whodunnit # => "me"
+    #   end
+    #
     # @api public
-    def whodunnit
-      paper_trail_store[:whodunnit]
+    def whodunnit(value = nil)
+      if value
+        raise ArgumentError, "no block given" unless block_given?
+
+        previous_whodunnit = paper_trail_store[:whodunnit]
+        paper_trail_store[:whodunnit] = value
+
+        begin
+          yield
+        ensure
+          paper_trail_store[:whodunnit] = previous_whodunnit
+        end
+      else
+        paper_trail_store[:whodunnit]
+      end
     end
 
     # Sets any information from the controller that you want PaperTrail to

spec/paper_trail_spec.rb

@@ -75,10 +75,31 @@ RSpec.describe PaperTrail do
   end
 
   describe ".whodunnit" do
-    before(:all) { described_class.whodunnit = "foobar" }
+    context "when set globally" do
+      before(:all) { described_class.whodunnit = "foobar" }
 
-    it "is nil by default" do
-      expect(described_class.whodunnit).to be_nil
+      it "is set to `nil` by default" do
+        expect(described_class.whodunnit).to be_nil
+      end
+    end
+
+    context "with block passed" do
+      it "sets whodunnit only for the block passed" do
+        described_class.whodunnit("foo") do
+          expect(described_class.whodunnit).to eq("foo")
+        end
+
+        expect(described_class.whodunnit).to be_nil
+      end
+
+      it "sets whodunnit only for the current thread" do
+        described_class.whodunnit("foo") do
+          expect(described_class.whodunnit).to eq("foo")
+          Thread.new { expect(described_class.whodunnit).to be_nil }.join
+        end
+
+        expect(described_class.whodunnit).to be_nil
+      end
     end
   end