chore(aggregation-mode): prevent rebuilding programs if not changed

aggregation_mode/Cargo.toml

@@ -29,6 +29,7 @@ risc0-ethereum-contracts = { git = "https://github.com/risc0/risc0-ethereum/", t
 [build-dependencies]
 sp1-build = { version = "4.1.3" } 
 risc0-build = { version = "2.0.0" }
+sha3 = "0.10.8"
 
 [package.metadata.risc0]
 # Tell risc0 build to find method in ./aggregation_programs/risc0 package

aggregation_mode/build.rs

@@ -1,15 +1,72 @@
 use risc0_build::{DockerOptionsBuilder, GuestOptionsBuilder};
+use sha3::{Digest, Keccak256};
+
 use std::collections::HashMap;
+use std::io::Read;
+use std::path::Path;
+use std::{env, fs};
+
+fn hash_files_and_features<P: AsRef<Path>>(paths: &[P], features: Vec<String>) -> String {
+    let mut hasher = Keccak256::new();
+    for path in paths {
+        let mut f = fs::File::open(path).unwrap();
+        let mut buffer = Vec::new();
+        f.read_to_end(&mut buffer).unwrap();
+        hasher.update(&buffer);
+    }
+
+    for feature in features {
+        hasher.update(&feature);
+    }
+
+    format!("{:x}", hasher.finalize())
+}
 
 // Reference: https://docs.succinct.xyz/docs/sp1/writing-programs/compiling#advanced-build-options-1
 fn main() {
+    let programs = [
+        "build.rs",
+        "aggregation_programs/Cargo.toml",
+        "aggregation_programs/Cargo.lock",
+        "aggregation_programs/sp1/Cargo.toml",
+        "aggregation_programs/sp1/src/lib.rs",
+        "aggregation_programs/sp1/src/user_proofs_aggregator_main.rs",
+        "aggregation_programs/sp1/src/chunk_aggregator_main.rs",
+        "aggregation_programs/risc0/Cargo.toml",
+        "aggregation_programs/risc0/src/user_proofs_aggregator_main.rs",
+        "aggregation_programs/risc0/src/chunk_aggregator_main.rs",
+        "aggregation_programs/risc0/src/lib.rs",
+    ];
+
+    for file in &programs {
+        println!("cargo:rerun-if-changed={}", file);
+    }
+
+    // Get all the env vars from rust (RUSTC, CARGO_FEATURES, etc)
+    // But filter those that don't affect the build of the program
+    let mut flags: Vec<String> = env::vars()
+        .filter(|(k, _)| k != "AGGREGATOR" || k != "RISC0_DEV_MODE" || k != "SP1_PROVER")
+        .map(|(k, v)| format!("{k}={v}"))
+        .collect();
+    // Sort them to make it deterministic in spite of the order.
+    flags.sort();
+
+    let hash = hash_files_and_features(&programs, flags);
+    let hash_file = Path::new("target/programs_hash.txt");
+
+    let needs_build = if let Ok(prev) = fs::read_to_string(hash_file) {
+        prev != hash
+    } else {
+        true
+    };
+
+    if !needs_build {
+        return;
+    }
+
     sp1_build::build_program_with_args("./aggregation_programs/sp1", {
         sp1_build::BuildArgs {
             output_directory: Some("./aggregation_programs/sp1/elf".to_string()),
-            binaries: vec![
-                "sp1_user_proofs_aggregator_program".into(),
-                "sp1_chunk_aggregator_program".into(),
-            ],
             // We use Docker to generate a reproducible ELF that will be identical across all platforms
             // (https://docs.succinct.xyz/docs/sp1/writing-programs/compiling#production-builds)
             docker: true,
@@ -25,9 +82,10 @@ fn main() {
         .use_docker(docker_options)
         .build()
         .unwrap();
-
     risc0_build::embed_methods_with_options(HashMap::from([(
         "risc0_aggregation_program",
         guest_options,
     )]));
+
+    fs::write(hash_file, hash).unwrap();
 }