It currently looks like the `map.get(element)` returns `undefined` even for previously-loaded elements. Are we evicting from the cache prematurely? Why?

Our second level caching (inside of `parseHookNames`) is working but this is still resulting in a lot of unnecessary work.
setPromises.push(
              new SourceMapConsumer(parsed).then(sourceConsumer => {
                hookSourceData.sourceConsumer = sourceConsumer;
              }),
            );
            break;
          }
        } else {
          if (sourceMappingURLs.length > 1) {
            console.warn(
              'More than one external source map detected in the source file',
            );
          }
          let url = sourceMappingURLs[i].split('=')[1];
          if (!url.startsWith('http') && !url.startsWith('/')) {
            
            const lastSlashIdx = runtimeSourceURL.lastIndexOf('/');
            if (lastSlashIdx !== -1) {
              const baseURL = runtimeSourceURL.slice(
                0,
                runtimeSourceURL.lastIndexOf('/'),
              );
              url = `${baseURL}/${url}`;
            }
          }
          hookSourceData.sourceMapURL = url;
          const fetchPromise =
            fetchPromises.get(url) ||
            fetchFile(url).then(
              sourceMapContents =>