Support arbitrarily nested Procs when setting/merging fields

lib/rackstash/fields/abstract_collection.rb

@@ -104,6 +104,8 @@ module Rackstash
       def resolve_value(value, scope: nil)
         return value unless value.is_a?(Proc)
         scope == nil ? value.call : scope.instance_exec(&value)
+      rescue
+        value.inspect
       end
 
       # Note: You should never mutate an array or hash returned by normalize
@@ -157,7 +159,7 @@ module Rackstash
           exception << "\n" << value.backtrace.join("\n") if value.backtrace
           return utf8_encode(exception)
         when ::Proc
-          return utf8_encode(value.inspect)
+          return normalize(value, scope: scope, wrap: wrap)
         when ::BigDecimal
           # A BigDecimal would be naturally represented as a JSON number. Most
           # libraries, however, parse non-integer JSON numbers directly as

lib/rackstash/fields/tags.rb

@@ -67,6 +67,8 @@ module Rackstash
           value = value.map { |tag| normalize_tags(tag, scope: scope) }
           value.flatten!
           value
+        elsif value.is_a?(Proc)
+          normalize_tags(value, scope: scope)
         elsif value.respond_to?(:to_ary)
           value = value.to_ary.map { |tag| normalize_tags(tag, scope: scope) }
           value.flatten!

spec/rackstash/fields/abstract_collection_spec.rb

@@ -489,18 +489,29 @@ describe Rackstash::Fields::AbstractCollection do
 
     describe 'with Proc' do
       it 'calls the proc by default and normalizes the result' do
-        proc = proc { :return }
+        proc = -> { :return }
 
         expect(normalize(proc)).to eql 'return'
         expect(normalize(proc).encoding).to eql Encoding::UTF_8
         expect(normalize(proc)).to be_frozen
       end
 
-      it 'inspects a nested proc' do
-        inner = proc { :return }
-        outer = proc { inner }
+      it 'calls a nested proc and normalizes the result' do
+        inner = -> { :return }
+        outer = -> { inner }
 
-        expect(normalize(outer)).to match %r{\A#<Proc:0x[0-9a-f]+@#{__FILE__}:#{__LINE__ - 3}>\z}
+        expect(normalize(outer)).to eql 'return'
+      end
+
+      it 'returns the inspected proc on errors' do
+        error = -> { raise 'Oh, no!' }
+        expected_arguments = ->(arg1, args, arg3) { 'cherio' }
+        ok = -> { :ok }
+        outer = -> { [ok, error, expected_arguments] }
+
+        expect(normalize(outer))
+          .to be_a(Rackstash::Fields::Array)
+          .and contain_exactly('ok', error.inspect, expected_arguments.inspect)
       end
     end