feat(forge build): cache project selectors by default

Calls `cache_local_signatures` function like the "forge selectors cache" command.

Author: mablr

crates/forge/src/cmd/build.rs

@@ -1,7 +1,10 @@
 use super::{install, watch::WatchArgs};
 use clap::Parser;
 use eyre::Result;
-use foundry_cli::{opts::BuildOpts, utils::LoadConfig};
+use foundry_cli::{
+    opts::BuildOpts,
+    utils::{cache_local_signatures, LoadConfig},
+};
 use foundry_common::{compile::ProjectCompiler, shell};
 use foundry_compilers::{
     compilers::{multi::MultiCompilerLanguage, Language},
@@ -100,6 +103,9 @@ impl BuildArgs {
 
         let output = compiler.compile(&project)?;
 
+        // Cache project selectors.
+        cache_local_signatures(&output, &Config::foundry_cache_dir().unwrap())?;
+
         if format_json && !self.names && !self.sizes {
             sh_println!("{}", serde_json::to_string_pretty(&output.output())?)?;
         }

crates/forge/tests/cli/test_cmd.rs

@@ -3828,3 +3828,41 @@ Encountered a total of 1 failing tests, 0 tests succeeded
 
 "#]]);
 });
+
+// This test is a copy of `error_event_decode_with_cache` in cast/tests/cli/selectors.rs
+// but it uses `forge build` to check that the project selectors are cached by default.
+forgetest_init!(build_with_selectors_cache, |prj, cmd| {
+    prj.add_source(
+        "LocalProjectContract",
+        r#"
+contract ContractWithCustomError {
+    error AnotherValueTooHigh(uint256, address);
+    event MyUniqueEventWithinLocalProject(uint256 a, address b);
+}
+   "#,
+    )
+    .unwrap();
+    // Build and cache project selectors.
+    cmd.forge_fuse().args(["build"]).assert_success();
+
+    // Assert cast can decode custom error with local cache.
+    cmd.cast_fuse()
+        .args(["decode-error", "0x7191bc6200000000000000000000000000000000000000000000000000000000000000650000000000000000000000000000000000000000000000000000000000D0004F"])
+        .assert_success()
+        .stdout_eq(str![[r#"
+AnotherValueTooHigh(uint256,address)
+101
+0x0000000000000000000000000000000000D0004F
+
+"#]]);
+    // Assert cast can decode event with local cache.
+    cmd.cast_fuse()
+        .args(["decode-event", "0xbd3699995dcc867b64dbb607be2c33be38df9134bef1178df13bfb9446e73104000000000000000000000000000000000000000000000000000000000000004e00000000000000000000000000000000000000000000000000000dd00000004e"])
+        .assert_success()
+        .stdout_eq(str![[r#"
+MyUniqueEventWithinLocalProject(uint256,address)
+78
+0x00000000000000000000000000000DD00000004e
+
+"#]]);
+});