From 1bd7111819fe442c7b15ec45dd05f88c6ad18737 Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Mon, 4 Sep 2023 19:30:36 +0100
Subject: [PATCH] chore(ci): add mocked backend binary to improve
 `compile_success_empty` tests (#2554)

---
 Cargo.lock                                    | 50 +++++++++++++++++++
 crates/acvm_backend_barretenberg/src/lib.rs   | 16 +++---
 crates/nargo_cli/Cargo.toml                   |  2 +
 crates/nargo_cli/build.rs                     | 12 ++++-
 .../test-binaries/mock_backend/Cargo.lock     |  7 +++
 .../test-binaries/mock_backend/Cargo.toml     | 10 ++++
 .../test-binaries/mock_backend/src/main.rs    | 10 ++++
 crates/nargo_cli/tests/execute.rs             |  2 +
 8 files changed, 98 insertions(+), 11 deletions(-)
 create mode 100644 crates/nargo_cli/test-binaries/mock_backend/Cargo.lock
 create mode 100644 crates/nargo_cli/test-binaries/mock_backend/Cargo.toml
 create mode 100644 crates/nargo_cli/test-binaries/mock_backend/src/main.rs

diff --git a/Cargo.lock b/Cargo.lock
index 76a9d98e23c..a2d00ee6cde 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -588,6 +588,38 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "89b2fd2a0dcf38d7971e2194b6b6eebab45ae01067456a7fd93d5547a61b70be"
 
+[[package]]
+name = "camino"
+version = "1.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c59e92b5a388f549b863a7bea62612c09f24c8393560709a54558a9abdfb3b9c"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "cargo-platform"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2cfa25e60aea747ec7e1124f238816749faa93759c6ff5b31f1ccdda137f4479"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "cargo_metadata"
+version = "0.15.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eee4243f1f26fc7a42710e7439c149e2b10b05472f88090acce52632f231a73a"
+dependencies = [
+ "camino",
+ "cargo-platform",
+ "semver",
+ "serde",
+ "serde_json",
+ "thiserror",
+]
+
 [[package]]
 name = "cast"
 version = "0.3.0"
@@ -2179,6 +2211,7 @@ dependencies = [
  "color-eyre",
  "const_format",
  "criterion",
+ "dirs",
  "fm",
  "hex",
  "iai",
@@ -2199,6 +2232,7 @@ dependencies = [
  "serde_json",
  "tempdir",
  "termcolor",
+ "test-binary",
  "thiserror",
  "tokio",
  "tokio-util",
@@ -3248,6 +3282,9 @@ name = "semver"
 version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b0293b4b29daaf487284529cc2f5675b8e57c61f70167ba415a463651fd6a918"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "serde"
@@ -3687,6 +3724,19 @@ version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3369f5ac52d5eb6ab48c6b4ffdc8efbcad6b89c765749064ba298f2c68a16a76"
 
+[[package]]
+name = "test-binary"
+version = "3.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb28771e7854f02e5705f2a1b09451d932a273f5a4ec1c9fa4c65882b8b7b6ca"
+dependencies = [
+ "camino",
+ "cargo_metadata",
+ "once_cell",
+ "paste",
+ "thiserror",
+]
+
 [[package]]
 name = "thiserror"
 version = "1.0.43"
diff --git a/crates/acvm_backend_barretenberg/src/lib.rs b/crates/acvm_backend_barretenberg/src/lib.rs
index 9f327ad8398..77e028bf30d 100644
--- a/crates/acvm_backend_barretenberg/src/lib.rs
+++ b/crates/acvm_backend_barretenberg/src/lib.rs
@@ -17,7 +17,7 @@ pub fn backends_directory() -> PathBuf {
 
 #[cfg(test)]
 fn get_bb() -> Backend {
-    let bb = Backend::default();
+    let bb = Backend::new("acvm-backend-barretenberg".to_string());
     crate::assert_binary_exists(&bb);
     bb
 }
@@ -36,12 +36,6 @@ pub struct Backend {
     name: String,
 }
 
-impl Default for Backend {
-    fn default() -> Self {
-        Self { name: "acvm-backend-barretenberg".to_string() }
-    }
-}
-
 impl Backend {
     pub fn new(name: String) -> Backend {
         Backend { name }
@@ -52,9 +46,13 @@ impl Backend {
     }
 
     fn binary_path(&self) -> PathBuf {
-        const BINARY_NAME: &str = "backend_binary";
+        if let Some(binary_path) = std::env::var_os("NARGO_BACKEND_PATH") {
+            PathBuf::from(binary_path)
+        } else {
+            const BINARY_NAME: &str = "backend_binary";
 
-        self.backend_directory().join(BINARY_NAME)
+            self.backend_directory().join(BINARY_NAME)
+        }
     }
 }
 
diff --git a/crates/nargo_cli/Cargo.toml b/crates/nargo_cli/Cargo.toml
index 466d34e1df1..c5bf646af18 100644
--- a/crates/nargo_cli/Cargo.toml
+++ b/crates/nargo_cli/Cargo.toml
@@ -54,6 +54,7 @@ tokio-util = { version = "0.7.8", features = ["compat"] }
 
 [dev-dependencies]
 tempdir = "0.3.7"
+dirs.workspace = true
 assert_cmd = "2.0.8"
 assert_fs = "1.0.10"
 predicates = "2.1.5"
@@ -66,6 +67,7 @@ pprof = { version = "0.12", features = [
     "criterion",
 ] }
 iai = "0.1.1"
+test-binary = "3.0.1"
 
 [[bench]]
 name = "criterion"
diff --git a/crates/nargo_cli/build.rs b/crates/nargo_cli/build.rs
index 42e0e318bfb..ad8988fba8e 100644
--- a/crates/nargo_cli/build.rs
+++ b/crates/nargo_cli/build.rs
@@ -104,15 +104,23 @@ fn generate_compile_success_empty_tests(test_file: &mut File, test_data_dir: &Pa
             r#"
 #[test]
 fn compile_success_empty_{test_name}() {{
-    let test_program_dir = PathBuf::from("{test_dir}");
+    
+    // We use a mocked backend for this test as we do not rely on the returned circuit size
+    // but we must call a backend as part of querying the number of opcodes in the circuit.
 
+    let test_program_dir = PathBuf::from("{test_dir}");
     let mut cmd = Command::cargo_bin("nargo").unwrap();
+    cmd.env("NARGO_BACKEND_PATH", path_to_mock_backend());
     cmd.arg("--program-dir").arg(test_program_dir);
     cmd.arg("info");
     cmd.arg("--json");
 
     let output = cmd.output().expect("Failed to execute command");
-    
+
+    if !output.status.success() {{
+        panic!("`nargo info` failed with: {{}}", String::from_utf8(output.stderr).unwrap());
+    }}
+
     // `compile_success_empty` tests should be able to compile down to an empty circuit.
     let json: serde_json::Value = serde_json::from_slice(&output.stdout).expect("JSON was not well-formatted");
     let num_opcodes = &json["programs"][0]["acir_opcodes"];
diff --git a/crates/nargo_cli/test-binaries/mock_backend/Cargo.lock b/crates/nargo_cli/test-binaries/mock_backend/Cargo.lock
new file mode 100644
index 00000000000..fd23780289a
--- /dev/null
+++ b/crates/nargo_cli/test-binaries/mock_backend/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "mock_backend"
+version = "0.1.0"
diff --git a/crates/nargo_cli/test-binaries/mock_backend/Cargo.toml b/crates/nargo_cli/test-binaries/mock_backend/Cargo.toml
new file mode 100644
index 00000000000..25528c7a6af
--- /dev/null
+++ b/crates/nargo_cli/test-binaries/mock_backend/Cargo.toml
@@ -0,0 +1,10 @@
+[workspace]
+
+[package]
+name = "mock_backend"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/crates/nargo_cli/test-binaries/mock_backend/src/main.rs b/crates/nargo_cli/test-binaries/mock_backend/src/main.rs
new file mode 100644
index 00000000000..3d2cd9f79b0
--- /dev/null
+++ b/crates/nargo_cli/test-binaries/mock_backend/src/main.rs
@@ -0,0 +1,10 @@
+#![forbid(unsafe_code)]
+#![warn(unreachable_pub)]
+#![warn(clippy::semicolon_if_nothing_returned)]
+#![cfg_attr(not(test), warn(unused_crate_dependencies, unused_extern_crates))]
+
+use std::io::Write;
+
+fn main() {
+    std::io::stdout().write_all(&0u64.to_be_bytes()).unwrap();
+}
diff --git a/crates/nargo_cli/tests/execute.rs b/crates/nargo_cli/tests/execute.rs
index e53ad068c01..664e9ad6a39 100644
--- a/crates/nargo_cli/tests/execute.rs
+++ b/crates/nargo_cli/tests/execute.rs
@@ -13,6 +13,8 @@ mod tests {
 
     use super::*;
 
+    test_binary::build_test_binary_once!(mock_backend, "test-binaries");
+
     // include tests generated by `build.rs`
     include!(concat!(env!("OUT_DIR"), "/execute.rs"));
 }