feat(forge): --watch coverage (#9702)

Author: yash-atreya

crates/forge/bin/cmd/coverage.rs

@@ -1,4 +1,4 @@
-use super::{install, test::TestArgs};
+use super::{install, test::TestArgs, watch::WatchArgs};
 use alloy_primitives::{map::HashMap, Address, Bytes, U256};
 use clap::{Parser, ValueEnum, ValueHint};
 use eyre::{Context, Result};
@@ -319,6 +319,14 @@ impl CoverageArgs {
         }
         Ok(())
     }
+
+    pub(crate) fn is_watch(&self) -> bool {
+        self.test.is_watch()
+    }
+
+    pub(crate) fn watch(&self) -> &WatchArgs {
+        &self.test.watch
+    }
 }
 
 /// Coverage reports to generate.

crates/forge/bin/cmd/watch.rs

@@ -1,8 +1,11 @@
-use super::{build::BuildArgs, doc::DocArgs, snapshot::GasSnapshotArgs, test::TestArgs};
+use super::{
+    build::BuildArgs, coverage::CoverageArgs, doc::DocArgs, snapshot::GasSnapshotArgs,
+    test::TestArgs,
+};
 use alloy_primitives::map::HashSet;
 use clap::Parser;
 use eyre::Result;
-use foundry_cli::utils::{self, FoundryPathExt};
+use foundry_cli::utils::{self, FoundryPathExt, LoadConfig};
 use foundry_config::Config;
 use parking_lot::Mutex;
 use std::{
@@ -316,6 +319,15 @@ pub async fn watch_test(args: TestArgs) -> Result<()> {
     Ok(())
 }
 
+pub async fn watch_coverage(args: CoverageArgs) -> Result<()> {
+    let config = args.load_config();
+    let config = args.watch().watchexec_config(|| [config.test, config.src])?;
+
+    run(config).await?;
+
+    Ok(())
+}
+
 /// Executes a [`Watchexec`] that listens for changes in the project's sources directory
 pub async fn watch_doc(args: DocArgs) -> Result<()> {
     let src_path = args.config()?.src;

crates/forge/bin/main.rs

@@ -49,7 +49,13 @@ fn run() -> Result<()> {
             }
         }
         ForgeSubcommand::Script(cmd) => utils::block_on(cmd.run_script()),
-        ForgeSubcommand::Coverage(cmd) => utils::block_on(cmd.run()),
+        ForgeSubcommand::Coverage(cmd) => {
+            if cmd.is_watch() {
+                utils::block_on(watch::watch_coverage(cmd))
+            } else {
+                utils::block_on(cmd.run())
+            }
+        }
         ForgeSubcommand::Bind(cmd) => cmd.run(),
         ForgeSubcommand::Build(cmd) => {
             if cmd.is_watch() {