fix(forge): disable artifacts for coverage (#9692)

* feat(`forge`): diff artifacts dir for coverage

* nit

* nit

* flip `no_artifacts` to true

* nit

crates/forge/bin/cmd/coverage.rs

@@ -107,7 +107,8 @@ impl CoverageArgs {
     /// Builds the project.
     fn build(&self, config: &Config) -> Result<(Project, ProjectCompileOutput)> {
         // Set up the project
-        let mut project = config.create_project(false, false)?;
+        let mut project = config.create_project(false, true)?;
+
         if self.ir_minimum {
             // print warning message
             sh_warn!("{}", concat!(
@@ -138,6 +139,13 @@ impl CoverageArgs {
             project.settings.solc.optimizer.details = None;
             project.settings.solc.via_ir = None;
         }
+        let mut warning =
+            "optimizer settings have been disabled for accurate coverage reports".to_string();
+        if !self.ir_minimum {
+            warning += ", if you encounter \"stack too deep\" errors, consider using `--ir-minimum` which enables viaIR with minimum optimization resolving most of the errors";
+        }
+
+        sh_warn!("{warning}")?;
 
         let output = ProjectCompiler::default()
             .compile(&project)?

crates/forge/tests/cli/coverage.rs

@@ -1,4 +1,4 @@
-use foundry_common::fs;
+use foundry_common::fs::{self, files_with_ext};
 use foundry_test_utils::{
     snapbox::{Data, IntoData},
     TestCommand, TestProject,
@@ -1691,3 +1691,63 @@ contract AContract {
 fn assert_lcov(cmd: &mut TestCommand, data: impl IntoData) {
     cmd.args(["--report=lcov", "--report-file"]).assert_file(data.into_data());
 }
+
+forgetest!(no_artifacts_written, |prj, cmd| {
+    prj.insert_ds_test();
+    prj.add_source(
+        "AContract.sol",
+        r#"
+contract AContract {
+    int public i;
+
+    function init() public {
+        i = 0;
+    }
+
+    function foo() public {
+        i = 1;
+    }
+}
+    "#,
+    )
+    .unwrap();
+
+    prj.add_source(
+        "AContractTest.sol",
+        r#"
+import "./test.sol";
+import {AContract} from "./AContract.sol";
+
+contract AContractTest is DSTest {
+    AContract a;
+
+    function setUp() public {
+        a = new AContract();
+        a.init();
+    }
+
+    function testFoo() public {
+        a.foo();
+    }
+}
+    "#,
+    )
+    .unwrap();
+
+    cmd.forge_fuse().arg("coverage").assert_success().stdout_eq(str![[r#"
+...
+╭-------------------+---------------+---------------+---------------+---------------╮
+| File              | % Lines       | % Statements  | % Branches    | % Funcs       |
++===================================================================================+
+| src/AContract.sol | 100.00% (4/4) | 100.00% (2/2) | 100.00% (0/0) | 100.00% (2/2) |
+|-------------------+---------------+---------------+---------------+---------------|
+| Total             | 100.00% (4/4) | 100.00% (2/2) | 100.00% (0/0) | 100.00% (2/2) |
+╰-------------------+---------------+---------------+---------------+---------------╯
+...
+"#]]);
+
+    // no artifacts are to be written
+    let files = files_with_ext(prj.artifacts(), "json").collect::<Vec<_>>();
+
+    assert!(files.is_empty());
+});