Add a non-interactive probe mode to `node inspect` for inspecting
runtime values in a run-to-completion application. This allows
users to perform printf-style debugging without having to modify
the application code and clean up afterwards, it also supports
structured output to be consumed by tools.
Probe mode launches the application, sets one or more source
breakpoints, evaluates one expression at each hit, and prints a
single text or JSON report when execution ends.
Interface:
node inspect [--json] [--preview] [--timeout=<ms>] [--port=<port>]
--probe <file>:<line>[:<col>] --expr <expr> ...
[--] <script> [args...]
Example:
```js
// cli.js
let maxRSS = 0;
for (let i = 0; i < 2; i++) {
const { rss } = process.memoryUsage();
maxRSS = Math.max(maxRSS, rss);
}
```
```
$ node inspect --probe cli.js:5 --expr 'rss' cli.js
Hit 1 at cli.js:5
rss = 54935552
Hit 2 at cli.js:5
rss = 55083008
Completed
```
(Prettified JSON to fit in commit message restrictions).
```js
$ node inspect --json --probe cli.js:5 --expr 'rss' cli.js
{"v":1,"probes":[{"expr":"rss","target":["cli.js",5]}],
"results":[
{"probe":0,"event":"hit","hit":1,
"result":{"type":"number","value":55443456,
"description":"55443456"}},
{"probe":0,"event":"hit","hit":2,
"result":{"type":"number","value":55574528,
"description":"55574528"}},
{"event":"completed"}]}
```
Signed-off-by: Joyee Cheung <joyeec9h3@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/62713
Reviewed-By: Jan Martin <jan.krems@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
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