Add flag to see storage diff if idemptotent check fails (#78)

When the idempotent migration check fails, users see this unhelpful
error message:

```
❌ Migrations are not idempotent. Selectively remove migrations from Executive until you find the culprit.
```

This PR implements a flag to enable printing the differences in storage.
It is disabled by default because users can ignore the "idempotent"
warning if they want to. If the flag is disabled there is a log that
suggests enabling it, improving the old message.

![Captura desde 2024-02-20
13-59-48](https://github.com/paritytech/try-runtime-cli/assets/44604217/1ae51887-6d26-411a-8874-23924b5cb536)

---------

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>

Author: 3 people

Cargo.lock

@@ -4,7 +4,7 @@ resolver = "2"
 members = ["cli", "core"]
 
 [workspace.package]
-version = "0.5.4"
+version = "0.6.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 description = "Substrate's programmatic testing framework."
 edition = "2021"

Cargo.toml

@@ -53,6 +53,7 @@ sp-weights = { workspace = true }
 
 substrate-rpc-client = { workspace = true }
 paris = "1.5.15"
+similar-asserts = "1.5.0"
 
 [dev-dependencies]
 assert_cmd = { workspace = true }

core/Cargo.toml

@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::{fmt::Debug, str::FromStr};
+use std::{collections::BTreeMap, fmt::Debug, str::FromStr};
 
 use bytesize::ByteSize;
 use frame_try_runtime::UpgradeCheckSelect;
@@ -24,7 +24,7 @@ use parity_scale_codec::Encode;
 use sc_executor::sp_wasm_interface::HostFunctions;
 use sp_core::{hexdisplay::HexDisplay, Hasher};
 use sp_runtime::traits::{Block as BlockT, HashingFor, NumberFor};
-use sp_state_machine::{CompactProof, StorageProof};
+use sp_state_machine::{CompactProof, OverlayedChanges, StorageProof};
 
 use crate::{
     build_executor,
@@ -69,6 +69,11 @@ pub struct Command {
     /// Whether to disable migration idempotency checks
     #[clap(long, default_value = "false", default_missing_value = "true")]
     pub disable_idempotency_checks: bool,
+
+    /// When migrations are detected as not idempotent, enabling this will output a diff of the
+    /// storage before and after running the same set of migrations the second time.
+    #[clap(long, default_value = "false", default_missing_value = "true")]
+    pub print_storage_diff: bool,
 }
 
 // Runs the `on-runtime-upgrade` command.
@@ -187,6 +192,7 @@ where
                 colorize_string("<bold><blue>-------------------------------------------------------------------")
             );
             let (oc_pre_root, _) = overlayed_changes.storage_root(&ext.backend, ext.state_version);
+            overlayed_changes.start_transaction();
             match state_machine_call_with_proof::<Block, HostFns>(
                 &ext,
                 &mut overlayed_changes,
@@ -202,6 +208,21 @@ where
                         overlayed_changes.storage_root(&ext.backend, ext.state_version);
                     if oc_pre_root != oc_post_root {
                         log::error!("❌ Migrations are not idempotent. Selectively remove migrations from Executive until you find the culprit.");
+                        if command.print_storage_diff {
+                            log::info!("Changed storage keys:");
+                            let changes_after =
+                                collect_storage_changes_as_hex::<Block>(&overlayed_changes);
+                            overlayed_changes.rollback_transaction().expect(
+                                "Migrations must not rollback transactions that they did not open",
+                            );
+                            let changes_before =
+                                collect_storage_changes_as_hex::<Block>(&overlayed_changes);
+
+                            similar_asserts::assert_eq!(changes_before, changes_after);
+                        } else {
+                            log::error!("Run with --print-storage-diff to see list of changed storage keys.");
+                        }
+
                         false
                     } else {
                         // Exeuction was OK and state root didn't change
@@ -366,3 +387,17 @@ fn analyse_ref_time(ref_time_results: RefTimeInfo, no_weight_warnings: bool) ->
         WeightSafety::ProbablySafe
     }
 }
+
+fn collect_storage_changes_as_hex<Block: BlockT>(
+    overlayed_changes: &OverlayedChanges<HashingFor<Block>>,
+) -> BTreeMap<String, String> {
+    overlayed_changes
+        .changes()
+        .filter_map(|(key, entry)| {
+            Some((
+                HexDisplay::from(key).to_string(),
+                HexDisplay::from(entry.value_ref().as_ref()?).to_string(),
+            ))
+        })
+        .collect()
+}