fix: Ignore max-age and s-maxage directives without a value

lib/faraday/http_cache/cache_control.rb

@@ -34,9 +34,9 @@ def no_store?
 
       # Internal: Gets the 'max-age' directive as an Integer.
       #
-      # Returns nil if the 'max-age' directive isn't present.
+      # Returns nil if the 'max-age' directive isn't present or has no value.
       def max_age
-        @directives['max-age'].to_i if @directives.key?('max-age')
+        integer_directive('max-age')
       end
 
       # Internal: Gets the 'max-age' directive as an Integer.
@@ -45,16 +45,16 @@ def max_age
       # if present to account for having to remove static age header when caching responses
       def normalize_max_ages(age)
         if age > 0
-          @directives['max-age'] = @directives['max-age'].to_i - age if @directives.key?('max-age')
-          @directives['s-maxage'] = @directives['s-maxage'].to_i - age if @directives.key?('s-maxage')
+          @directives['max-age'] = max_age - age if max_age
+          @directives['s-maxage'] = shared_max_age - age if shared_max_age
         end
       end
 
       # Internal: Gets the 's-maxage' directive as an Integer.
       #
-      # Returns nil if the 's-maxage' directive isn't present.
+      # Returns nil if the 's-maxage' directive isn't present or has no value.
       def shared_max_age
-        @directives['s-maxage'].to_i if @directives.key?('s-maxage')
+        integer_directive('s-maxage')
       end
       alias s_maxage shared_max_age
 
@@ -70,13 +70,10 @@ def proxy_revalidate?
 
       # Internal: Gets the 'stale-while-revalidate' directive as an Integer.
       #
-      # Returns nil if the 'stale-while-revalidate' directive isn't present, or
-      # assigned as boolean.
+      # Returns nil if the 'stale-while-revalidate' directive isn't present or
+      # has no value.
       def stale_while_revalidate
-        return unless @directives.key?('stale-while-revalidate')
-        return if @directives['stale-while-revalidate'] == true
-
-        @directives['stale-while-revalidate'].to_i
+        integer_directive('stale-while-revalidate')
       end
 
       # Internal: Gets the String representation for the cache directives.
@@ -102,6 +99,16 @@ def to_s
 
       private
 
+      # Internal: Reads a directive whose value must be an integer.
+      # A directive given without a value (a bare 'max-age') is parsed as
+      # true; treat it as absent instead of calling to_i on it.
+      #
+      # Returns the Integer value, or nil.
+      def integer_directive(name)
+        value = @directives[name]
+        value.to_i unless value.nil? || value == true
+      end
+
       # Internal: Parses the Cache Control string to a Hash.
       # Existing whitespace will be removed and the string is split on commas.
       # For each part everything before a '=' will be treated as the key

spec/cache_control_spec.rb

@@ -52,6 +52,23 @@
     expect(cache_control.shared_max_age).to eq(600)
   end
 
+  it 'responds to #max_age with nil when the max-age directive has no value' do
+    cache_control = Faraday::HttpCache::CacheControl.new('public, max-age')
+    expect(cache_control.max_age).to be_nil
+  end
+
+  it 'responds to #shared_max_age with nil when the s-maxage directive has no value' do
+    cache_control = Faraday::HttpCache::CacheControl.new('public, s-maxage')
+    expect(cache_control.shared_max_age).to be_nil
+  end
+
+  it 'normalizes max ages without raising when a directive has no value' do
+    cache_control = Faraday::HttpCache::CacheControl.new('max-age, s-maxage=600')
+    cache_control.normalize_max_ages(100)
+    expect(cache_control.max_age).to be_nil
+    expect(cache_control.shared_max_age).to eq(500)
+  end
+
   it 'responds to #shared_max_age with nil when no s-maxage directive present' do
     cache_control = Faraday::HttpCache::CacheControl.new('public')
     expect(cache_control.shared_max_age).to be_nil