inspector: add --cond to node inspect probe mode#64328
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On a hot path, the probe can record every hit and require
filtering afterwards. This patch adds a per-probe `--cond <expr>`
option that allows limiting the hit to only when the expression
is truthy at the probe location. V8 evaluates it as the breakpoint's
native condition, so the target is not paused when it does not hold,
and a condition that throws is treated as false. Since in CDP,
a location can only carry one breakpoint per URL pattern,
probes sharing a location must share one condition (or none).
Conflicting conditions are rejected.
Example:
```js
// app.js
let total = 0;
for (let i = 0; i < 10; i++) {
total += i; // line 4
}
```
```
$ out/Release/node inspect --probe app.js:4 --expr 'total' \
--cond 'i % 3 === 0' app.js
```
```
Hit 1 at file:///path/to/app.js:3:3
total = 0
Hit 2 at file:///path/to/app.js:3:3
total = 3
Hit 3 at file:///path/to/app.js:3:3
total = 15
Hit 4 at file:///path/to/app.js:3:3
total = 36
Completed
```
Signed-off-by: Joyee Cheung <joyeec9h3@gmail.com>
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Jul 7, 2026
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Jul 7, 2026
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|
Thanks for the review, I think I've addressed the comments. @jasnell can you take another look? Thanks! |
jasnell
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Jul 8, 2026
Codecov Reportβ
All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #64328 +/- ##
==========================================
- Coverage 92.01% 90.25% -1.76%
==========================================
Files 379 741 +362
Lines 166972 241221 +74249
Branches 25554 45436 +19882
==========================================
+ Hits 153639 217716 +64077
- Misses 13041 15077 +2036
- Partials 292 8428 +8136
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Commit Queue failed- Loading data for nodejs/node/pull/64328 β Done loading data for nodejs/node/pull/64328 ----------------------------------- PR info ------------------------------------ Title inspector: add --cond to node inspect probe mode (#64328) Author Joyee Cheung <joyeec9h3@gmail.com> (@joyeecheung) Branch joyeecheung:probe-cond -> nodejs:main Labels needs-ci, debugger, commit-queue-squash Commits 2 - inspector: add --cond to node inspect probe mode - fixup! inspector: add --cond to node inspect probe mode Committers 1 - Joyee Cheung <joyeec9h3@gmail.com> PR-URL: https://github.com/nodejs/node/pull/64328 Refs: https://github.com/nodejs/node/issues/63646 Reviewed-By: James M Snell <jasnell@gmail.com> ------------------------------ Generated metadata ------------------------------ PR-URL: https://github.com/nodejs/node/pull/64328 Refs: https://github.com/nodejs/node/issues/63646 Reviewed-By: James M Snell <jasnell@gmail.com> -------------------------------------------------------------------------------- βΉ This PR was created on Mon, 06 Jul 2026 16:11:06 GMT β Approvals: 1 β - James M Snell (@jasnell) (TSC): https://github.com/nodejs/node/pull/64328#pullrequestreview-4655834114 β This PR needs to wait 2 more hours to land (or 0 minutes if there is one more approval) β Last GitHub CI successful βΉ Last Full PR CI on 2026-07-13T09:07:38Z: https://ci.nodejs.org/job/node-test-pull-request/74776/ - Querying data for job/node-test-pull-request/74776/ β Build data downloaded β Last Jenkins CI successful -------------------------------------------------------------------------------- β Aborted `git node land` session in /home/runner/work/node/node/.ncuhttps://github.com/nodejs/node/actions/runs/29260446092 |
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On a hot path, the probe can record every hit and require filtering afterwards. This patch adds a per-probe
--cond <expr>option that allows limiting the hit to only when the expression is truthy at the probe location. V8 evaluates it as the breakpoint's native condition, so the target is not paused when it does not hold, and a condition that throws is treated as false. Since in CDP, a location can only carry one breakpoint per URL pattern, probes sharing a location must share one condition (or none). Conflicting conditions are rejected.Example:
Refs: #63646