fix: handle cache body file not existing when using etag (#22931)

cli/file_fetcher.rs

@@ -14,6 +14,7 @@ use crate::util::progress_bar::ProgressBar;
 use crate::util::progress_bar::UpdateGuard;
 
 use deno_ast::MediaType;
+use deno_core::anyhow::bail;
 use deno_core::anyhow::Context;
 use deno_core::error::custom_error;
 use deno_core::error::generic_error;
@@ -372,6 +373,7 @@ impl FileFetcher {
     }
 
     async move {
+      let mut maybe_etag = maybe_etag;
       let mut retried = false;
       let result = loop {
         let result = match fetch_once(
@@ -388,9 +390,23 @@ impl FileFetcher {
         {
           FetchOnceResult::NotModified => {
             let file = file_fetcher
-              .fetch_cached(&specifier, maybe_checksum, 10)?
-              .unwrap();
-            Ok(file)
+              .fetch_cached(&specifier, maybe_checksum.clone(), 10)?;
+            match file {
+              Some(file) => Ok(file),
+              None => {
+                // Someone may have deleted the body from the cache since
+                // it's currently stored in a separate file from the headers,
+                // so delete the etag and try again
+                if maybe_etag.is_some() {
+                  debug!("Cache body not found. Trying again without etag.");
+                  maybe_etag = None;
+                  continue;
+                } else {
+                  // should never happen
+                  bail!("Your deno cache directory is in an unrecoverable state. Please delete it and try again.")
+                }
+              }
+            }
           }
           FetchOnceResult::Redirect(redirect_url, headers) => {
             file_fetcher.http_cache.set(&specifier, headers, &[])?;

tests/integration/run_tests.rs

@@ -5137,3 +5137,36 @@ console.log(add(3, 4));
   let output = test_context.new_command().args("run main.ts").run();
   output.assert_matches_text("[WILDCARD]5\n7\n");
 }
+
+#[test]
+fn run_etag_delete_source_cache() {
+  let test_context = TestContextBuilder::new()
+    .use_temp_cwd()
+    .use_http_server()
+    .build();
+  test_context
+    .temp_dir()
+    .write("main.ts", "import 'http://localhost:4545/etag_script.ts'");
+  test_context
+    .new_command()
+    .args("cache main.ts")
+    .run()
+    .skip_output_check();
+
+  // The cache is currently stored unideally in two files where one file has the headers
+  // and the other contains the body. An issue can happen with the etag header where the
+  // headers file exists, but the body was deleted. We need to get the cache to gracefully
+  // handle this scenario.
+  let deno_dir = test_context.deno_dir().path();
+  let etag_script_path = deno_dir.join("deps/http/localhost_PORT4545/26110db7d42c9bad32386735cbc05c301f83e4393963deb8da14fec3b4202a13");
+  assert!(etag_script_path.exists());
+  etag_script_path.remove_file();
+
+  test_context
+    .new_command()
+    .args("cache --reload --log-level=debug main.ts")
+    .run()
+    .assert_matches_text(
+      "[WILDCARD]Cache body not found. Trying again without etag.[WILDCARD]",
+    );
+}