Fix some internal errors in filters from invalid input. (#1476)

These fixes came from improving the corresponding test, so these might not
actually be causing problems in practice.

History.md

@@ -1,5 +1,11 @@
 # Liquid Change Log
 
+## 5.1.1 (unreleased)
+
+### Fixes
+
+* Fix some internal errors in filters from invalid input [Dylan Thacker-Smith]
+
 ## 5.1.0 / 2021-09-09
 
 ### Features

lib/liquid/standardfilters.rb

@@ -213,17 +213,23 @@ module Liquid
 
       if ary.empty?
         []
-      elsif ary.first.respond_to?(:[]) && target_value.nil?
-        begin
-          ary.select { |item| item[property] }
+      elsif target_value.nil?
+        ary.select do |item|
+          item[property]
         rescue TypeError
           raise_property_error(property)
+        rescue NoMethodError
+          return nil unless item.respond_to?(:[])
+          raise
         end
-      elsif ary.first.respond_to?(:[])
-        begin
-          ary.select { |item| item[property] == target_value }
+      else
+        ary.select do |item|
+          item[property] == target_value
         rescue TypeError
           raise_property_error(property)
+        rescue NoMethodError
+          return nil unless item.respond_to?(:[])
+          raise
         end
       end
     end
@@ -237,11 +243,14 @@ module Liquid
         ary.uniq
       elsif ary.empty? # The next two cases assume a non-empty array.
         []
-      elsif ary.first.respond_to?(:[])
-        begin
-          ary.uniq { |a| a[property] }
+      else
+        ary.uniq do |item|
+          item[property]
         rescue TypeError
           raise_property_error(property)
+        rescue NoMethodError
+          return nil unless item.respond_to?(:[])
+          raise
         end
       end
     end
@@ -277,11 +286,14 @@ module Liquid
         ary.compact
       elsif ary.empty? # The next two cases assume a non-empty array.
         []
-      elsif ary.first.respond_to?(:[])
-        begin
-          ary.reject { |a| a[property].nil? }
+      else
+        ary.reject do |item|
+          item[property].nil?
         rescue TypeError
           raise_property_error(property)
+        rescue NoMethodError
+          return nil unless item.respond_to?(:[])
+          raise
         end
       end
     end
@@ -486,10 +498,16 @@ module Liquid
     end
 
     def nil_safe_compare(a, b)
-      if !a.nil? && !b.nil?
-        a <=> b
+      result = a <=> b
+
+      if result
+        result
+      elsif a.nil?
+        1
+      elsif b.nil?
+        -1
       else
-        a.nil? ? 1 : -1
+        raise Liquid::ArgumentError, "cannot sort values of incompatible types"
       end
     end
 

test/integration/standard_filter_test.rb

@@ -259,8 +259,8 @@ class StandardFiltersTest < Minitest::Test
       { "price" => 1, "handle" => "gamma" },
       { "price" => 2, "handle" => "epsilon" },
       { "price" => 4, "handle" => "alpha" },
-      { "handle" => "delta" },
       { "handle" => "beta" },
+      { "handle" => "delta" },
     ]
     assert_equal(expectation, @filters.sort(input, "price"))
   end
@@ -852,19 +852,14 @@ class StandardFiltersTest < Minitest::Test
       { 1 => "bar" },
       ["foo", 123, nil, true, false, Drop, ["foo"], { foo: "bar" }],
     ]
-    test_types.each do |first|
-      test_types.each do |other|
-        (@filters.methods - Object.methods).each do |method|
-          arg_count = @filters.method(method).arity
-          arg_count *= -1 if arg_count < 0
-          inputs = [first]
-          inputs << ([other] * (arg_count - 1)) if arg_count > 1
-          begin
-            @filters.send(method, *inputs)
-          rescue Liquid::ArgumentError, Liquid::ZeroDivisionError
-            nil
-          end
-        end
+    StandardFilters.public_instance_methods(false).each do |method|
+      arg_count = @filters.method(method).arity
+      arg_count *= -1 if arg_count < 0
+
+      test_types.repeated_permutation(arg_count) do |args|
+        @filters.send(method, *args)
+      rescue Liquid::Error
+        nil
       end
     end
   end