Mark configs with unique id. Use id for provisioner caching.

plugins/commands/serve/mappers/config_data.rb

@@ -127,6 +127,12 @@ module VagrantPlugins
             end
           end
 
+          # Include a unique identifier for this configuration instance. This
+          # will allow us to identifier it later when it is decoded.
+          if !data.key?("_vagrant_config_identifier")
+            data["_vagrant_config_identifier"] = SecureRandom.uuid
+          end
+
           entries = data.map do |k, v|
             begin
               SDK::Args::HashEntry.new(

plugins/commands/serve/service/provisioner_service.rb

@@ -75,10 +75,13 @@ module VagrantPlugins
         end
 
         def load_provisioner(klass, machine, config)
-          key = cache.key(klass, machine)
-          return cache.get(key) if cache.registered?(key)
+          ident = config.instance_variable_get(:@_vagrant_config_identifier)
+          if ident
+            key = cache.key(klass, machine, ident)
+            return cache.get(key) if cache.registered?(key)
+          end
           klass.new(machine, config).tap do |i|
-            cache.register(key, i)
+            cache.register(key, i) if key
           end
         end
       end

plugins/commands/serve/util/direct_conversions.rb

@@ -1,5 +1,6 @@
 # Patch things to produce proto messages
 require "pathname"
+require "securerandom"
 require "google/protobuf/wrappers_pb"
 require "google/protobuf/well_known_types"
 
@@ -147,6 +148,12 @@ class Vagrant::Plugin::V2::Config
       end
     end
 
+    # Include a unique identifier for this configuration instance. This
+    # will allow us to identifier it later when it is decoded.
+    if !data.key?("_vagrant_config_identifier")
+      data["_vagrant_config_identifier"] = SecureRandom.uuid
+    end
+
     entries = data.map do |k, v|
       Hashicorp::Vagrant::Sdk::Args::HashEntry.new(
         key: k.to_any,