fix: do not panic linting files with UTF-8 BOM (#24136)

Closes #24122

Cargo.toml

@@ -43,7 +43,7 @@ license = "MIT"
 repository = "https://github.com/denoland/deno"
 
 [workspace.dependencies]
-deno_ast = { version = "=0.39.0", features = ["transpiling"] }
+deno_ast = { version = "=0.39.1", features = ["transpiling"] }
 deno_core = { version = "0.284.0" }
 
 deno_bench_util = { version = "0.149.0", path = "./bench_util" }

cli/tools/lint/mod.rs

@@ -230,7 +230,7 @@ async fn lint_files(
     deno_core::unsync::spawn(async move {
       run_parallelized(paths, {
         move |file_path| {
-          let file_text = fs::read_to_string(&file_path)?;
+          let file_text = deno_ast::strip_bom(fs::read_to_string(&file_path)?);
 
           // don't bother rechecking this file if it didn't have any diagnostics before
           if incremental_cache.is_file_same(&file_path, &file_text) {
@@ -510,7 +510,7 @@ fn lint_stdin(
   linter
     .lint_file(LintFileOptions {
       specifier: specifier_from_file_path(file_path)?,
-      source_code: source_code.clone(),
+      source_code: deno_ast::strip_bom(source_code),
       media_type: MediaType::TypeScript,
       config,
     })

tests/specs/lint/bom/__test__.jsonc

@@ -0,0 +1,5 @@
+{
+  "args": "lint mod.ts",
+  "exitCode": 1,
+  "output": "mod.out"
+}

tests/specs/lint/bom/mod.out

@@ -0,0 +1,12 @@
+error[no-unused-vars]: `t` is never used
+ --> [WILDLINE]
+  | 
+4 | const t = 5;
+  |       ^
+  = hint: If this is intentional, prefix it with an underscore like `_t`
+
+  docs: https://lint.deno.land/rules/no-unused-vars
+
+
+Found 1 problem
+Checked 1 file

tests/specs/lint/bom/mod.ts

@@ -0,0 +1,4 @@
+// this file is saved as UTF8 with BOM
+console.log("Hello, world!");
+
+const t = 5;