From bd2381f764f8f7d31c95b522fe70779b0b887dc4 Mon Sep 17 00:00:00 2001
From: Peter Hedenskog <phedenskog@wikimedia.org>
Date: Tue, 19 May 2026 15:21:37 +0200
Subject: [PATCH] Fix the CDP field name for render-blocking lift
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  The lift introduced in 1.3.0 silently never fires against real
  Chrome. Chrome emits the per-request render-blocking classification
  as Network.requestWillBeSent.params.renderBlockingBehavior, not
  renderBlockingStatus — _renderBlocking was therefore unset on
  every entry, and every downstream consumer (waterfall-tools' orange
  ⊗ marker, sitespeed.io's request detail panel, pagexray's
  render-blocking counts) silently rendered nothing.

  The synthetic unit tests passed against the typo because they
  authored the input next to the assertion; a regression test against
  a real perflog now guards that class of mistake.

Co-authored-by: Claude Opus 4.7 (1M context) noreply@anthropic.com
---
 index.js      | 17 +++++++++--------
 test/tests.js | 25 +++++++++++++++++++++----
 2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/index.js b/index.js
index 6c47a2b..a4f4aeb 100644
--- a/index.js
+++ b/index.js
@@ -226,14 +226,15 @@ export function harFromMessages(messages, options) {
             _resourceType: params.type ? params.type.toLowerCase() : undefined
           };
 
-          // CDP `renderBlockingStatus` (Chrome 108+) — values are PascalCase
-          // (`Blocking`, `NonBlocking`, `InBodyParserBlocking`, `Potentially…`).
-          // waterfall-tools' WPT-style renderer matches `_renderBlocking ===
-          // 'blocking'` to draw the orange ⊗ marker, so lowercase the value
-          // here. Other variants ride along verbatim-lowercased for any
-          // consumer that wants to inspect them.
-          if (params.renderBlockingStatus) {
-            entry._renderBlocking = params.renderBlockingStatus.toLowerCase();
+          // CDP per-request render-blocking classification (Chrome 108+).
+          // The field lives at `Network.requestWillBeSent.params.renderBlockingBehavior`
+          // and its values are PascalCase (`Blocking`, `NonBlocking`,
+          // `NonBlockingDynamic`, …). waterfall-tools' WPT-style renderer
+          // matches `_renderBlocking === 'blocking'` to draw the orange ⊗
+          // marker, so lowercase the value here; other variants ride along
+          // verbatim-lowercased for any consumer that wants to inspect them.
+          if (params.renderBlockingBehavior) {
+            entry._renderBlocking = params.renderBlockingBehavior.toLowerCase();
           }
 
           // The object initiator change according to its type
diff --git a/test/tests.js b/test/tests.js
index e61039d..04bf18f 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -130,13 +130,13 @@ test('Parses IPv6 address', t => {
   );
 });
 
-test('Lifts CDP renderBlockingStatus onto entries as `_renderBlocking`', t => {
+test('Lifts CDP renderBlockingBehavior onto entries as `_renderBlocking`', t => {
   // Minimal synthetic CDP stream: one render-blocking document + one
   // non-blocking subresource. The renderer in waterfall-tools matches
   // `_renderBlocking === 'blocking'` (lowercase) to draw the orange ⊗
   // marker, so we assert the casing here too.
   const frameId = 'F1';
-  const baseMessages = (requestId, url, renderBlockingStatus) => [
+  const baseMessages = (requestId, url, renderBlockingBehavior) => [
     {
       method: 'Network.requestWillBeSent',
       params: {
@@ -154,7 +154,7 @@ test('Lifts CDP renderBlockingStatus onto entries as `_renderBlocking`', t => {
         wallTime: 1_700_000_000,
         initiator: { type: 'other' },
         type: requestId === '1' ? 'Document' : 'Script',
-        ...(renderBlockingStatus ? { renderBlockingStatus } : {})
+        ...(renderBlockingBehavior ? { renderBlockingBehavior } : {})
       }
     },
     {
@@ -208,7 +208,7 @@ test('Lifts CDP renderBlockingStatus onto entries as `_renderBlocking`', t => {
 });
 
 test('Omits `_renderBlocking` when CDP did not report it', t => {
-  // Older Chrome builds don't emit renderBlockingStatus at all — make sure
+  // Older Chrome builds don't emit renderBlockingBehavior at all — make sure
   // we don't materialise the field as `undefined` or an empty string in
   // that case. Absent input → absent output.
   const messages = [
@@ -270,6 +270,23 @@ test('Omits `_renderBlocking` when CDP did not report it', t => {
   t.false('_renderBlocking' in har.log.entries[0]);
 });
 
+test('Lifts `_renderBlocking` from a real Chrome perflog', t => {
+  // Regression guard against the field-name typo this test file was first
+  // shipped with (`renderBlockingStatus` vs. the real CDP field
+  // `renderBlockingBehavior`). The synthetic tests above can't catch that
+  // class of mistake — they'd silently pass against either spelling
+  // because they author the input alongside the assertion. A real Chrome
+  // perflog can.
+  const perflogPath = perflog('soft-navigation-github-issues.json');
+  return parsePerflog(perflogPath).then(har => {
+    const values = new Set(
+      har.log.entries.map(e => e._renderBlocking).filter(v => v !== undefined)
+    );
+    t.true(values.has('nonblocking'));
+    t.true(values.has('nonblockingdynamic'));
+  });
+});
+
 test('Forwards the resource type value', t => {
   const perflogPath = perflog('www.google.ru.json');
   const expected = {