Use symbol instead of weak map for associating data with contexts

[szegedi]

What does this PR do?

Binds profiler event specific data into context objects using a symbol instead of using a WeakMap.

Motivation

As discussed in #6267, the WeakMap solution strongly referenced the callback context object (the key in the map) from the value. Binding the data we need to track in a symbol property of the context object itself solves this problem.

As an additional bonus, since the context object is passed to the finish method we no longer need to keep track of it in start, reducing the data set to only the event start time. This way, we could eliminate the need for an intermediate object for storing the tuple of { startEvent, startTime }.

Additional info

I took the opportunity to also introduce private fields in the EventPlugin class – this is broken into its own commit for ease of review.

[github-actions]

Overall package size

Self size: 11.35 MB
Deduped: 111 MB
No deduping: 111.39 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | @datadog/libdatadog | 0.7.0 | 35.02 MB | 35.02 MB | | @datadog/native-appsec | 10.1.0 | 20.37 MB | 20.37 MB | | @datadog/native-iast-taint-tracking | 4.0.0 | 11.72 MB | 11.73 MB | | @datadog/pprof | 5.9.0 | 9.77 MB | 10.14 MB | | @opentelemetry/core | 1.30.1 | 908.66 kB | 7.16 MB | | protobufjs | 7.5.3 | 2.95 MB | 5.6 MB | | @datadog/wasm-js-rewriter | 4.0.1 | 2.85 MB | 3.58 MB | | @datadog/native-metrics | 3.1.1 | 1.02 MB | 1.43 MB | | @opentelemetry/api | 1.8.0 | 1.21 MB | 1.21 MB | | jsonpath-plus | 10.3.0 | 617.18 kB | 1.08 MB | | import-in-the-middle | 1.14.2 | 122.36 kB | 850.93 kB | | lru-cache | 10.4.3 | 804.3 kB | 804.3 kB | | source-map | 0.7.4 | 226 kB | 226 kB | | opentracing | 0.14.7 | 194.81 kB | 194.81 kB | | pprof-format | 2.1.0 | 111.69 kB | 111.69 kB | | @datadog/sketches-js | 2.1.1 | 109.9 kB | 109.9 kB | | lodash.sortby | 4.7.0 | 75.76 kB | 75.76 kB | | ignore | 7.0.5 | 63.38 kB | 63.38 kB | | istanbul-lib-coverage | 3.2.2 | 34.37 kB | 34.37 kB | | rfdc | 1.4.1 | 27.15 kB | 27.15 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB | | @isaacs/ttlcache | 1.4.1 | 25.2 kB | 25.2 kB | | tlhunter-sorted-set | 0.1.0 | 24.94 kB | 24.94 kB | | shell-quote | 1.8.3 | 23.74 kB | 23.74 kB | | limiter | 1.1.5 | 23.17 kB | 23.17 kB | | retry | 0.13.1 | 18.85 kB | 18.85 kB | | semifies | 1.0.0 | 15.84 kB | 15.84 kB | | jest-docblock | 29.7.0 | 8.99 kB | 12.76 kB | | crypto-randomuuid | 1.0.0 | 11.18 kB | 11.18 kB | | ttl-set | 1.0.0 | 4.61 kB | 9.69 kB | | mutexify | 1.4.0 | 5.71 kB | 8.74 kB | | path-to-regexp | 0.1.12 | 6.6 kB | 6.6 kB | | koalas | 1.0.2 | 6.47 kB | 6.47 kB | | module-details-from-path | 1.0.4 | 3.96 kB | 3.96 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.95%. Comparing base (092a702) to head (a5bd5f9).

Files with missing lines	Patch %	Lines
...ace/src/profiling/profilers/event_plugins/event.js	78.57%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6276      +/-   ##
==========================================
- Coverage   83.97%   82.95%   -1.02%     
==========================================
  Files         471      462       -9     
  Lines       19516    19571      +55     
==========================================
- Hits        16388    16235     -153     
- Misses       3128     3336     +208     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-08-13 12:07:34

Comparing candidate commit a5bd5f9 in PR branch szegedi/no-weakmap-in-events with baseline commit 092a702 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1271 metrics, 52 unstable metrics.

[BridgeAR]

Nice change! LGTM