fix(nargo): correct inconsistent file extension for ACIR hashes (#994)

* Made `save_and_preprocess_program` public for the crate

* Rename extension (`json.sha256`->`json.checksum`)

Idk which you prefer though

* Add integration test for the "cached use case flow"

By "cached use case flow" I mean the user proving and verifying over a circuit that was compiled using `nargo compile <circuit_name>`

* Add test helper function

* cargo fmt

* Both integration tests cannot run in parallel

* Add `ACIR_CHECKSUM` extension constant

* Test that fetching pk & vk works as expected

* Rollback integration test

* Rollback needless logic

* cargo fmt

* Extend test

Now it also checks that the keys it returns are the ones that we saved

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>

* Fix test & format

---------

Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>

crates/nargo/src/cli/fs/keys.rs

@@ -1,13 +1,10 @@
-use std::path::{Path, PathBuf};
-
-use acvm::{acir::circuit::Circuit, hash_constraint_system};
-
+use super::{create_named_dir, load_hex_data, write_to_file};
 use crate::{
-    constants::{PK_EXT, VK_EXT},
+    constants::{ACIR_CHECKSUM, PK_EXT, VK_EXT},
     errors::CliError,
 };
-
-use super::{create_named_dir, load_hex_data, write_to_file};
+use acvm::{acir::circuit::Circuit, hash_constraint_system};
+use std::path::{Path, PathBuf};
 
 pub(crate) fn save_key_to_dir<P: AsRef<Path>>(
     key: Vec<u8>,
@@ -32,7 +29,7 @@ pub(crate) fn fetch_pk_and_vk<P: AsRef<Path>>(
     check_proof: bool,
 ) -> Result<(Vec<u8>, Vec<u8>), CliError> {
     let mut acir_hash_path = PathBuf::from(circuit_build_path.as_ref());
-    acir_hash_path.set_extension("json.checksum");
+    acir_hash_path.set_extension(ACIR_CHECKSUM);
 
     let expected_acir_hash = load_hex_data(acir_hash_path.clone())?;
 
@@ -66,3 +63,30 @@ pub(crate) fn fetch_pk_and_vk<P: AsRef<Path>>(
 
     Ok((proving_key, verification_key))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::fetch_pk_and_vk;
+    use crate::cli::fs::{keys::save_key_to_dir, program::save_acir_hash_to_dir};
+    use acvm::acir::circuit::Circuit;
+    use tempdir::TempDir;
+
+    #[test]
+    fn fetching_pk_and_vk_loads_expected_keys() {
+        let circuit = Circuit::default();
+        let circuit_name = "my_circuit";
+        let mut circuit_build_path = TempDir::new("temp_circuit_hash_dir").unwrap().into_path();
+
+        // These values are not meaningful, we just need distinct values.
+        let pk: Vec<u8> = vec![0];
+        let vk: Vec<u8> = vec![1, 2];
+        save_key_to_dir(pk.clone(), circuit_name, &circuit_build_path, true).unwrap();
+        save_key_to_dir(vk.clone(), circuit_name, &circuit_build_path, false).unwrap();
+
+        save_acir_hash_to_dir(&circuit, circuit_name, &circuit_build_path);
+        circuit_build_path.push(circuit_name);
+
+        let loaded_keys = fetch_pk_and_vk(&circuit, circuit_build_path, true, true).unwrap();
+        assert_eq!(loaded_keys, (pk, vk));
+    }
+}

crates/nargo/src/cli/fs/program.rs

@@ -3,7 +3,7 @@ use std::path::{Path, PathBuf};
 use acvm::{acir::circuit::Circuit, hash_constraint_system};
 use noirc_driver::CompiledProgram;
 
-use crate::errors::CliError;
+use crate::{constants::ACIR_CHECKSUM, errors::CliError};
 
 use super::{create_named_dir, write_to_file};
 
@@ -27,7 +27,7 @@ pub(crate) fn save_acir_hash_to_dir<P: AsRef<Path>>(
     hash_dir: P,
 ) -> PathBuf {
     let acir_hash = hash_constraint_system(circuit);
-    let hash_path = hash_dir.as_ref().join(hash_name).with_extension("json.sha256");
+    let hash_path = hash_dir.as_ref().join(hash_name).with_extension(ACIR_CHECKSUM);
     write_to_file(hex::encode(acir_hash).as_bytes(), &hash_path);
 
     hash_path

crates/nargo/src/constants.rs

@@ -25,3 +25,5 @@ pub(crate) const WITNESS_EXT: &str = "tr";
 pub(crate) const PK_EXT: &str = "pk";
 /// The extension for verification keys.
 pub(crate) const VK_EXT: &str = "vk";
+/// The extension for ACIR hash files.
+pub(crate) const ACIR_CHECKSUM: &str = "json.checksum";