perf(core) Reduce script name and script code copies (#18298)

Reduce the number of copies and allocations of script code by carrying
around ownership/reference information from creation time.

As an advantage, this allows us to maintain the identity of `&'static
str`-based scripts and use v8's external 1-byte strings (to avoid
incorrectly passing non-ASCII strings, debug `assert!`s gate all string
reference paths).

Benchmark results:

Perf improvements -- ~0.1 - 0.2ms faster, but should reduce garbage
w/external strings and reduces data copies overall. May also unlock some
more interesting optimizations in the future.

This requires adding some generics to functions, but manual
monomorphization has been applied (outer/inner function) to avoid code
bloat.

1 files changed, 13 insertions, 11 deletions

diff --git a/cli/tools/coverage/mod.rs b/cli/tools/coverage/mod.rs
index eaa087171..9fead6e37 100644
--- a/cli/tools/coverage/mod.rs
+++ b/cli/tools/coverage/mod.rs
@@ -20,6 +20,7 @@ use deno_core::serde_json;
 use deno_core::sourcemap::SourceMap;
 use deno_core::url::Url;
 use deno_core::LocalInspectorSession;
+use deno_core::ModuleCode;
 use regex::Regex;
 use std::fs;
 use std::fs::File;
@@ -170,16 +171,16 @@ struct CoverageReport {
 
 fn generate_coverage_report(
   script_coverage: &ScriptCoverage,
-  script_source: &str,
+  script_source: String,
   maybe_source_map: &Option<Vec<u8>>,
   output: &Option<PathBuf>,
 ) -> CoverageReport {
   let maybe_source_map = maybe_source_map
     .as_ref()
     .map(|source_map| SourceMap::from_slice(source_map).unwrap());
-  let text_lines = TextLines::new(script_source);
+  let text_lines = TextLines::new(&script_source);
 
-  let comment_ranges = deno_ast::lex(script_source, MediaType::JavaScript)
+  let comment_ranges = deno_ast::lex(&script_source, MediaType::JavaScript)
     .into_iter()
     .filter(|item| {
       matches!(item.inner, deno_ast::TokenOrComment::Comment { .. })
@@ -680,14 +681,14 @@ pub async fn cover_files(
     })?;
 
     // Check if file was transpiled
-    let original_source = &file.source;
-    let transpiled_code = match file.media_type {
+    let original_source = file.source.clone();
+    let transpiled_code: ModuleCode = match file.media_type {
       MediaType::JavaScript
       | MediaType::Unknown
       | MediaType::Cjs
       | MediaType::Mjs
-      | MediaType::Json => file.source.as_ref().to_string(),
-      MediaType::Dts | MediaType::Dmts | MediaType::Dcts => "".to_string(),
+      | MediaType::Json => file.source.into(),
+      MediaType::Dts | MediaType::Dmts | MediaType::Dcts => Default::default(),
       MediaType::TypeScript
       | MediaType::Jsx
       | MediaType::Mts
@@ -695,7 +696,7 @@ pub async fn cover_files(
       | MediaType::Tsx => {
         let source_hash = get_source_hash(&file.source, ps.emit_options_hash);
         match ps.emit_cache.get_emit_code(&file.specifier, source_hash) {
-          Some(code) => code,
+          Some(code) => code.into(),
           None => {
             return Err(anyhow!(
               "Missing transpiled source code for: \"{}\".
@@ -710,15 +711,16 @@ pub async fn cover_files(
       }
     };
 
+    let source_map = source_map_from_code(&transpiled_code);
     let coverage_report = generate_coverage_report(
       &script_coverage,
-      &transpiled_code,
-      &source_map_from_code(&transpiled_code),
+      transpiled_code.take_as_string(),
+      &source_map,
       &out_mode,
     );
 
     if !coverage_report.found_lines.is_empty() {
-      reporter.report(&coverage_report, original_source)?;
+      reporter.report(&coverage_report, &original_source)?;
     }
   }