feat(build): add option to build specific dir

crates/cli/src/opts/build/core.rs

@@ -126,6 +126,11 @@ pub struct CoreBuildArgs {
     #[serde(skip)]
     pub skip: Option<Vec<SkipBuildFilter>>,
 
+    /// Build source files from specified paths.
+    #[arg(long, short, num_args(0..))]
+    #[serde(skip)]
+    pub paths: Option<Vec<PathBuf>>,
+
     #[command(flatten)]
     #[serde(flatten)]
     pub compiler: CompilerArgs,

crates/forge/bin/cmd/build.rs

@@ -3,7 +3,11 @@ use clap::Parser;
 use eyre::Result;
 use foundry_cli::{opts::CoreBuildArgs, utils::LoadConfig};
 use foundry_common::compile::ProjectCompiler;
-use foundry_compilers::{Project, ProjectCompileOutput};
+use foundry_compilers::{
+    compilers::{multi::MultiCompilerLanguage, Language},
+    utils::source_files_iter,
+    Project, ProjectCompileOutput,
+};
 use foundry_config::{
     figment::{
         self,
@@ -80,7 +84,16 @@ impl BuildArgs {
 
         let project = config.project()?;
 
+        // Collect sources to compile if build subdirectories specified.
+        let mut files = vec![];
+        if let Some(dirs) = self.args.paths {
+            for dir in dirs {
+                files.extend(source_files_iter(dir, MultiCompilerLanguage::FILE_EXTENSIONS));
+            }
+        }
+
         let compiler = ProjectCompiler::new()
+            .files(files)
             .print_names(self.names)
             .print_sizes(self.sizes)
             .quiet(self.format_json)

crates/forge/tests/cli/cmd.rs

@@ -1667,6 +1667,69 @@ function test_run() external {}
     );
 });
 
+forgetest_init!(can_build_specific_paths, |prj, cmd| {
+    prj.wipe();
+    prj.add_source(
+        "Counter.sol",
+        r"
+contract Counter {
+function count() external {}
+}",
+    )
+    .unwrap();
+    prj.add_test(
+        "Foo.sol",
+        r"
+contract Foo {
+function test_foo() external {}
+}",
+    )
+    .unwrap();
+    prj.add_test(
+        "Bar.sol",
+        r"
+contract Bar {
+function test_bar() external {}
+}",
+    )
+    .unwrap();
+
+    // Build 2 files within test dir
+    prj.clear();
+    cmd.args(["build", "--paths", "test", "--force"]);
+    cmd.unchecked_output().stdout_matches_path(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/can_build_path_with_two_files.stdout"),
+    );
+
+    // Build one file within src dir
+    prj.clear();
+    cmd.forge_fuse();
+    cmd.args(["build", "--paths", "src", "--force"]);
+    cmd.unchecked_output().stdout_matches_path(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/can_build_path_with_one_file.stdout"),
+    );
+
+    // Build 3 files from test and src dirs
+    prj.clear();
+    cmd.forge_fuse();
+    cmd.args(["build", "--paths", "src", "test", "--force"]);
+    cmd.unchecked_output().stdout_matches_path(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/can_build_path_with_three_files.stdout"),
+    );
+
+    // Build single test file
+    prj.clear();
+    cmd.forge_fuse();
+    cmd.args(["build", "--paths", "test/Bar.sol", "--force"]);
+    cmd.unchecked_output().stdout_matches_path(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/can_build_path_with_one_file.stdout"),
+    );
+});
+
 // checks that build --sizes includes all contracts even if unchanged
 forgetest_init!(can_build_sizes_repeatedly, |prj, cmd| {
     prj.clear_cache();

crates/forge/tests/fixtures/can_build_path_with_one_file.stdout

@@ -0,0 +1,3 @@
+Compiling 1 files with 0.8.23
+Solc 0.8.23 finished in 33.25ms
+Compiler run successful!

crates/forge/tests/fixtures/can_build_path_with_three_files.stdout

@@ -0,0 +1,3 @@
+Compiling 3 files with 0.8.23
+Solc 0.8.23 finished in 33.25ms
+Compiler run successful!

crates/forge/tests/fixtures/can_build_path_with_two_files.stdout

@@ -0,0 +1,3 @@
+Compiling 2 files with 0.8.23
+Solc 0.8.23 finished in 33.25ms
+Compiler run successful!