Return reason of why proof cant be generated (api change) (#2389)

## Linked Issues/PRs
Additional changes related to
#1394
Closes: #2367

## Description
Initially we
[wanted](#2258 (review))
these changes, but eventually
[decided](#2258 (comment))
to
[revert](#2258 (comment))
them from the original PR, because even though they are
[not](#2258 (comment))
[considered](#2258 (comment))
strictly breaking, they change the API.



## Checklist
- [X] Breaking changes are clearly marked as such in the PR description
and changelog

### Before requesting review
- [X] I have reviewed the code myself

CHANGELOG.md

@@ -32,6 +32,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - [2378](https://github.com/FuelLabs/fuel-core/pull/2378): Use cached hash of the topic instead of calculating it on each publishing gossip message.
 
+#### Breaking
+- [2389](https://github.com/FuelLabs/fuel-core/pull/2258): Updated the `messageProof` GraphQL schema to return a non-nullable `MessageProof`.
+
 ## [Version 0.40.0]
 
 ### Added

crates/client/assets/schema.sdl

@@ -980,7 +980,7 @@ type Query {
 		"""
 		owner: Address,		first: Int,		after: String,		last: Int,		before: String
 	): MessageConnection!
-	messageProof(transactionId: TransactionId!, nonce: Nonce!, commitBlockId: BlockId, commitBlockHeight: U32): MessageProof
+	messageProof(transactionId: TransactionId!, nonce: Nonce!, commitBlockId: BlockId, commitBlockHeight: U32): MessageProof!
 	messageStatus(nonce: Nonce!): MessageStatus!
 	relayedTransactionStatus(
 		"""

crates/client/src/client.rs

@@ -1141,7 +1141,7 @@ impl FuelClient {
         nonce: &Nonce,
         commit_block_id: Option<&BlockId>,
         commit_block_height: Option<BlockHeight>,
-    ) -> io::Result<Option<types::MessageProof>> {
+    ) -> io::Result<types::MessageProof> {
         let transaction_id: TransactionId = (*transaction_id).into();
         let nonce: schema::Nonce = (*nonce).into();
         let commit_block_id: Option<schema::BlockId> =
@@ -1153,14 +1153,7 @@ impl FuelClient {
             commit_block_id,
             commit_block_height,
         });
-
-        let proof = self
-            .query(query)
-            .await?
-            .message_proof
-            .map(TryInto::try_into)
-            .transpose()?;
-
+        let proof = self.query(query).await?.message_proof.try_into()?;
         Ok(proof)
     }
 

crates/client/src/client/schema/message.rs

@@ -114,7 +114,7 @@ pub struct MessageProofQuery {
         commitBlockId: $commit_block_id,
         commitBlockHeight: $commit_block_height
     )]
-    pub message_proof: Option<MessageProof>,
+    pub message_proof: MessageProof,
 }
 
 #[derive(cynic::QueryFragment, Clone, Debug)]

crates/fuel-core/src/schema/message.rs

@@ -136,7 +136,7 @@ impl MessageQuery {
         nonce: Nonce,
         commit_block_id: Option<BlockId>,
         commit_block_height: Option<U32>,
-    ) -> async_graphql::Result<Option<MessageProof>> {
+    ) -> async_graphql::Result<MessageProof> {
         let query = ctx.read_view()?;
         let height = match (commit_block_id, commit_block_height) {
             (Some(commit_block_id), None) => {
@@ -157,7 +157,7 @@ impl MessageQuery {
             height,
         )?;
 
-        Ok(Some(MessageProof(proof)))
+        Ok(MessageProof(proof))
     }
 
     #[graphql(complexity = "query_costs().storage_read + child_complexity")]

tests/tests/messages.rs

@@ -485,7 +485,6 @@ async fn can_get_message_proof() {
             let result = client
                 .message_proof(&transaction_id, nonce, None, Some(last_height))
                 .await
-                .unwrap()
                 .unwrap();
 
             // 1. Generate the message id (message fields)

tests/tests/regenesis.rs

@@ -401,8 +401,7 @@ async fn test_regenesis_message_proofs_are_preserved() -> anyhow::Result<()> {
         .client
         .message_proof(&tx_id, nonce, None, Some((message_block_height + 1).into()))
         .await
-        .expect("Unable to get message proof")
-        .expect("Message proof not found");
+        .expect("Unable to get message proof");
     let prev_root = proof.commit_block_header.prev_root;
     let block_proof_index = proof.block_proof.proof_index;
     let block_proof_set: Vec<_> = proof
@@ -460,8 +459,7 @@ async fn test_regenesis_message_proofs_are_preserved() -> anyhow::Result<()> {
             .client
             .message_proof(&tx_id, nonce, None, Some(block_height.into()))
             .await
-            .expect("Unable to get message proof")
-            .expect("Message proof not found");
+            .expect("Unable to get message proof");
         let prev_root = proof.commit_block_header.prev_root;
         let block_proof_set: Vec<_> = proof
             .block_proof