add dry_run meta

.gitignore

@@ -7,4 +7,5 @@
 
 tests/_*
 /*.move
-execute.sh
+execute.sh
+test.sh

executor/src/execution.rs

@@ -20,6 +20,8 @@ use crate::oracles::{oracle_coins_module, time_metadata};
 use move_vm_runtime::logging::NoContextLog;
 use crate::session::ConstsMap;
 
+pub type SerializedTransactionEffects = Vec<((AccountAddress, StructTag), Option<Vec<u8>>)>;
+
 #[derive(Debug, Default, Clone)]
 pub struct FakeRemoteCache {
     modules: HashMap<ModuleId, Vec<u8>>,
@@ -65,23 +67,36 @@ impl FakeRemoteCache {
         .to_owned())
     }
 
-    pub fn merge_transaction_effects(&mut self, effects: TransactionEffects) -> usize {
+    pub fn serialize_effects(
+        &self,
+        effects: TransactionEffects,
+    ) -> (SerializedTransactionEffects, usize) {
         let mut resources_write_size = 0;
+        let mut resources = vec![];
         for (addr, changes) in effects.resources {
             for (struct_tag, val) in changes {
                 match val {
                     Some((layout, val)) => {
                         let serialized = val.simple_serialize(&layout).expect("Valid value.");
                         resources_write_size += serialized.len();
-                        self.resources.insert((addr, struct_tag), serialized);
+                        resources.push(((addr, struct_tag), Some(serialized)));
                     }
                     None => {
-                        self.resources.remove(&(addr, struct_tag));
+                        resources.push(((addr, struct_tag), None));
                     }
                 }
             }
         }
-        resources_write_size
+        (resources, resources_write_size)
+    }
+
+    pub fn merge_effects(&mut self, serialized_effects: SerializedTransactionEffects) {
+        for ((addr, struct_tag), val) in serialized_effects {
+            match val {
+                Some(val) => self.resources.insert((addr, struct_tag), val),
+                None => self.resources.remove(&(addr, struct_tag)),
+            };
+        }
     }
 }
 
@@ -156,6 +171,7 @@ pub fn execute_script(
         oracle_prices,
         current_time,
         aborts_with,
+        dry_run,
         ..
     } = meta;
     if !oracle_prices.is_empty() {
@@ -190,8 +206,12 @@ pub fn execute_script(
     Ok(match res {
         Ok(effects) => {
             let mut explained = explain_effects(&effects, &ds)?;
-            let write_set_size = data_store.merge_transaction_effects(effects);
-            explained.set_write_set_size(write_set_size);
+            let (serialized_effects, effects_writeset_size) =
+                data_store.serialize_effects(effects);
+            explained.set_write_set_size(effects_writeset_size);
+            if !dry_run {
+                data_store.merge_effects(serialized_effects);
+            }
             StepExecutionResult::Success(explained)
         }
         Err(vm_error) => {

executor/src/meta.rs

@@ -24,6 +24,7 @@ pub struct ExecutionMeta {
     pub oracle_prices: Vec<(StructTag, u128)>,
     pub current_time: Option<u64>,
     pub aborts_with: Option<u64>,
+    pub dry_run: bool,
 }
 
 impl ExecutionMeta {
@@ -54,6 +55,7 @@ impl ExecutionMeta {
             }
             "current_time" => self.current_time = Some(val.parse().unwrap()),
             "aborts_with" => self.aborts_with = Some(val.parse().unwrap()),
+            "dry_run" => self.dry_run = val.parse().unwrap(),
             _ => eprintln!("Unimplemented meta key, {:?}", key),
         }
     }

executor/tests/test_executor.rs

@@ -915,3 +915,50 @@ fn test_extract_error_name_if_prefixed_with_err() {
         "Execution aborted with code 101: ERR_RECORD_DOES_NOT_EXIST in module 0x2::Record."
     );
 }
+
+#[test]
+fn test_dry_run_do_not_apply_writeset_changes() {
+    let _pool = ConstPool::new();
+    let text = r"
+script {
+    use 0x2::Record;
+
+    fun step_1(s: &signer) {
+        Record::create_record(s, 10);
+    }
+}
+
+/// dry_run: true
+script {
+    use 0x2::Record;
+
+    fun step_2(s: &signer) {
+        Record::increment_record(s);
+    }
+}
+
+script {
+    use 0x2::Record;
+
+    fun step_3(s: &signer) {
+        Record::increment_record(s);
+    }
+}
+    ";
+
+    let effects = execute_script(
+        MoveFile::with_content(script_path(), text),
+        vec![stdlib_mod("signer.move"), modules_mod("record.move")],
+        "libra",
+        "0x3",
+        vec![],
+    )
+    .unwrap()
+    .last()
+    .unwrap()
+    .effects();
+    assert_eq!(
+        effects.resources()[0].changes[0].1,
+        ResourceChange("0x2::Record::T".to_string(), Some("[U8(11)]".to_string()))
+    );
+}