Remove obsolete owner pays fee feature and XRPL_ABANDON stanza (#5550)

If a feature was never voted on then it is safe to remove.

include/xrpl/protocol/Feature.h

@@ -53,19 +53,19 @@
  *    then change the macro parameter in features.macro to
  *    `VoteBehavior::DefaultYes`. The communication process is beyond
  *    the scope of these instructions.
+
+ * 5) If a supported feature (`Supported::yes`) was _ever_ in a released
+ *     version, it can never be changed back to `Supported::no`, because
+ *     it _may_ still become enabled at any time. This would cause newer
+ *     versions of `rippled` to become amendment blocked.
+ *     Instead, to prevent newer versions from voting on the feature, use
+ *     `VoteBehavior::Obsolete`. Obsolete features can not be voted for
+ *     by any versions of `rippled` built with that setting, but will still
+ *     work correctly if they get enabled. If a feature remains obsolete
+ *     for long enough that _all_ clients that could vote for it are
+ *     amendment blocked, the feature can be removed from the code
+ *     as if it was unsupported.
  *
- * 5) A feature marked as Obsolete can mean either:
- *    1) It is in the ledger (marked as Supported::yes) and it is on its way to
- *      become Retired
- *    2) The feature is not in the ledger (has always been marked as
- *      Supported::no) and the code to support it has been removed
- *
- * If we want to discontinue a feature that we've never fully supported and
- * the feature has never been enabled, we should remove all the related
- * code, and mark the feature as "abandoned". To do this:
- *
- * 1) Open features.macro, move the feature to the abandoned section and
- *    change the macro to XRPL_ABANDON
  *
  * When a feature has been enabled for several years, the conditional code
  * may be removed, and the feature "retired". To retire a feature:
@@ -99,13 +99,10 @@ namespace detail {
 #undef XRPL_FIX
 #pragma push_macro("XRPL_RETIRE")
 #undef XRPL_RETIRE
-#pragma push_macro("XRPL_ABANDON")
-#undef XRPL_ABANDON
 
 #define XRPL_FEATURE(name, supported, vote) +1
 #define XRPL_FIX(name, supported, vote) +1
 #define XRPL_RETIRE(name) +1
-#define XRPL_ABANDON(name) +1
 
 // This value SHOULD be equal to the number of amendments registered in
 // Feature.cpp. Because it's only used to reserve storage, and determine how
@@ -122,8 +119,6 @@ static constexpr std::size_t numFeatures =
 #pragma pop_macro("XRPL_FIX")
 #undef XRPL_FEATURE
 #pragma pop_macro("XRPL_FEATURE")
-#undef XRPL_ABANDON
-#pragma pop_macro("XRPL_ABANDON")
 
 /** Amendments that this server supports and the default voting behavior.
    Whether they are enabled depends on the Rules defined in the validated
@@ -365,13 +360,10 @@ foreachFeature(FeatureBitset bs, F&& f)
 #undef XRPL_FIX
 #pragma push_macro("XRPL_RETIRE")
 #undef XRPL_RETIRE
-#pragma push_macro("XRPL_ABANDON")
-#undef XRPL_ABANDON
 
 #define XRPL_FEATURE(name, supported, vote) extern uint256 const feature##name;
 #define XRPL_FIX(name, supported, vote) extern uint256 const fix##name;
 #define XRPL_RETIRE(name)
-#define XRPL_ABANDON(name)
 
 #include <xrpl/protocol/detail/features.macro>
 
@@ -381,8 +373,6 @@ foreachFeature(FeatureBitset bs, F&& f)
 #pragma pop_macro("XRPL_FIX")
 #undef XRPL_FEATURE
 #pragma pop_macro("XRPL_FEATURE")
-#undef XRPL_ABANDON
-#pragma pop_macro("XRPL_ABANDON")
 
 }  // namespace ripple
 

include/xrpl/protocol/detail/features.macro

@@ -26,9 +26,6 @@
 #if !defined(XRPL_RETIRE)
 #error "undefined macro: XRPL_RETIRE"
 #endif
-#if !defined(XRPL_ABANDON)
-#error "undefined macro: XRPL_ABANDON"
-#endif
 
 // Add new amendments to the top of this list.
 // Keep it sorted in reverse chronological order.
@@ -133,11 +130,6 @@ XRPL_FIX    (NFTokenDirV1,          Supported::yes, VoteBehavior::Obsolete)
 XRPL_FEATURE(NonFungibleTokensV1,   Supported::yes, VoteBehavior::Obsolete)
 XRPL_FEATURE(CryptoConditionsSuite, Supported::yes, VoteBehavior::Obsolete)
 
-// The following amendments were never supported, never enabled, and 
-// we've abanded them. These features should never be in the ledger,
-// and we've removed all the related code.
-XRPL_ABANDON(OwnerPaysFee)
-
 // The following amendments have been active for at least two years. Their
 // pre-amendment code has been removed and the identifiers are deprecated.
 // All known amendments and amendments that may appear in a validated

src/libxrpl/protocol/Feature.cpp

@@ -254,7 +254,7 @@ FeatureCollections::registerFeature(
 {
     check(!readOnly, "Attempting to register a feature after startup.");
     check(
-        support == Supported::yes || vote != VoteBehavior::DefaultYes,
+        support == Supported::yes || vote == VoteBehavior::DefaultNo,
         "Invalid feature parameters. Must be supported to be up-voted.");
     Feature const* i = getByName(name);
     if (!i)
@@ -268,7 +268,7 @@ FeatureCollections::registerFeature(
         features.emplace_back(name, f);
 
         auto const getAmendmentSupport = [=]() {
-            if (vote == VoteBehavior::Obsolete && support == Supported::yes)
+            if (vote == VoteBehavior::Obsolete)
                 return AmendmentSupport::Retired;
             return support == Supported::yes ? AmendmentSupport::Supported
                                              : AmendmentSupport::Unsupported;
@@ -398,14 +398,6 @@ retireFeature(std::string const& name)
     return registerFeature(name, Supported::yes, VoteBehavior::Obsolete);
 }
 
-// Abandoned features are not in the ledger and have no code controlled by the
-// feature. They were never supported, and cannot be voted on.
-uint256
-abandonFeature(std::string const& name)
-{
-    return registerFeature(name, Supported::no, VoteBehavior::Obsolete);
-}
-
 /** Tell FeatureCollections when registration is complete. */
 bool
 registrationIsDone()
@@ -440,8 +432,6 @@ featureToName(uint256 const& f)
 #undef XRPL_FIX
 #pragma push_macro("XRPL_RETIRE")
 #undef XRPL_RETIRE
-#pragma push_macro("XRPL_ABANDON")
-#undef XRPL_ABANDON
 
 #define XRPL_FEATURE(name, supported, vote) \
     uint256 const feature##name = registerFeature(#name, supported, vote);
@@ -453,11 +443,6 @@ featureToName(uint256 const& f)
     [[deprecated("The referenced amendment has been retired")]] \
     [[maybe_unused]]                                            \
     uint256 const retired##name = retireFeature(#name);
-
-#define XRPL_ABANDON(name)                                        \
-    [[deprecated("The referenced amendment has been abandoned")]] \
-    [[maybe_unused]]                                              \
-    uint256 const abandoned##name = abandonFeature(#name);
 // clang-format on
 
 #include <xrpl/protocol/detail/features.macro>
@@ -468,8 +453,6 @@ featureToName(uint256 const& f)
 #pragma pop_macro("XRPL_FIX")
 #undef XRPL_FEATURE
 #pragma pop_macro("XRPL_FEATURE")
-#undef XRPL_ABANDON
-#pragma pop_macro("XRPL_ABANDON")
 
 // All of the features should now be registered, since variables in a cpp file
 // are initialized from top to bottom.