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cli: add --experimental build flag#62755

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ShogunPanda:experimental-flag
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cli: add --experimental build flag#62755
ShogunPanda wants to merge 1 commit intonodejs:mainfrom
ShogunPanda:experimental-flag

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@ShogunPanda ShogunPanda commented Apr 15, 2026 •
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This PR adds a new --experimental BUILD flag which can be used to turn ALL experimental features on by default.

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nodejs-github-bot commented Apr 15, 2026

Review requested:

  • @nodejs/config
  • @nodejs/inspector

@nodejs-github-bot nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels Apr 15, 2026
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aduh95 commented Apr 15, 2026

That seems like a bad idea; if you want to avoid long commands, use a config file, no?

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marco-ippolito commented Apr 15, 2026

why would you want to enable ALL experimental flags? It might have side effects the user is not aware of

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ShogunPanda commented Apr 15, 2026

I can document this to be very bad or dangerous.
But I find myself something struggling to remember all the experimental flags I need to enabled.
Also, one thing: can we please start treating users as adults: adding a global flag won't make the runtime more dangerous, to be honest.

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ShogunPanda commented Apr 15, 2026

That seems like a bad idea; if you want to avoid long commands, use a config file, no?

Just to enable a bunch of experimental flags you have to create a JSON file with schema and so forth. Seems to be a little overkill.

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marco-ippolito requested changes Apr 15, 2026
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Making my objection explicit. The node.config.json exists for this specific reason: improve the dx of having a lot of cli flags. I cannot think a use case where you want to enable all experimental flags. This might cause unexpected effects because the interaction between multiple experimental flag is untested. I'd rather have user write a json file than a dangerous "free for all flag"

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ShogunPanda commented Apr 15, 2026

@marco-ippolito I understand your concerns. I disagree, which is totally fine.
Do you think that explicitly stating that is dangerous and also listing out which flags it enables would lift your objection?

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aduh95 commented Apr 15, 2026

An alternative would be a build/configure flag, would that work for you?

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marco-ippolito commented Apr 15, 2026

An alternative would be a build/configure flag, would that work for you?

I'm fine with a build flag

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ShogunPanda commented Apr 15, 2026

An alternative would be a build/configure flag, would that work for you?

Do you mean a configure flag that enables the CLI flag on C++ side so that only people with custom build will see it?

If that's the idea, I'm up for it. Good idea. @marco-ippolito Would it solve your objection?

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ShogunPanda commented Apr 15, 2026

Amazing. Updating this soon.

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marco-ippolito commented Apr 15, 2026 •
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An alternative would be a build/configure flag, would that work for you?

Do you mean a configure flag that enables the CLI flag on C++ side so that only people with custom build will see it?

If that's the idea, I'm up for it. Good idea. @marco-ippolito Would it solve your objection?

yes, I'm fine with it, would be nice to actually have them enabled without a runtime flag (just the build flag) so you can run the test suite and test the interaction among all the experimental features.
This PR only enables an arbitrary subset of experimental features though, not all of them

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codecov bot commented Apr 15, 2026 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.69%. Comparing base (3f52482) to head (31ba820).

Additional details and impacted files 
@@            Coverage Diff             @@
##             main   #62755      +/-   ##
==========================================
- Coverage   91.55%   89.69%   -1.86%     
==========================================
  Files         356      706     +350     
  Lines      149601   218127   +68526     
  Branches    23395    41734   +18339     
==========================================
+ Hits       136967   195651   +58684     
- Misses      12371    14399    +2028     
- Partials      263     8077    +7814
Files with missing lines Coverage Δ
src/node_options.h 98.00% <100.00%> (ø)

... and 473 files with indirect coverage changes

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cli: add --experimental build flag
31ba820 
Signed-off-by: Paolo Insogna <paolo@cowtech.it>
@ShogunPanda ShogunPanda changed the title cli: add --experimental flag cli: add --experimental build flag Apr 15, 2026
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ShogunPanda commented Apr 15, 2026

@marco-ippolito @aduh95 Updated now. WDYT?

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aduh95 reviewed Apr 15, 2026
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Comment thread src/node_options.h
Comment on lines +131 to +137
EXPERIMENTAL_OPTION(experimental_addon_modules, false)
EXPERIMENTAL_OPTION(experimental_eventsource, false)
EXPERIMENTAL_OPTION(experimental_fetch, true)
EXPERIMENTAL_OPTION(experimental_ffi, false)
EXPERIMENTAL_OPTION(experimental_websocket, true)
EXPERIMENTAL_OPTION(experimental_sqlite, true)
EXPERIMENTAL_OPTION(experimental_stream_iter, false)
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@aduh95 aduh95 Apr 15, 2026 •
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Wouldn't it make more sense to have a EXPERIMENTAL_DISABLED_BY_DEFAULT be set to true or false? Seems more intent reveling to me

Suggested change
EXPERIMENTAL_OPTION(experimental_addon_modules, false)
EXPERIMENTAL_OPTION(experimental_eventsource, false)
EXPERIMENTAL_OPTION(experimental_fetch, true)
EXPERIMENTAL_OPTION(experimental_ffi, false)
EXPERIMENTAL_OPTION(experimental_websocket, true)
EXPERIMENTAL_OPTION(experimental_sqlite, true)
EXPERIMENTAL_OPTION(experimental_stream_iter, false)
bool experimental_addon_modules = EXPERIMENTAL_DISABLED_BY_DEFAULT;
bool experimental_eventsource = EXPERIMENTAL_DISABLED_BY_DEFAULT;
bool experimental_fetch = true;
bool experimental_ffi = EXPERIMENTAL_DISABLED_BY_DEFAULT;
bool experimental_websocket = EXPERIMENTAL_DISABLED_BY_DEFAULT;
bool experimental_sqlite = HAVE_SQLITE;
bool experimental_stream_iter = EXPERIMENTAL_DISABLED_BY_DEFAULT;

aduh95
aduh95 reviewed Apr 15, 2026
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Comment thread configure.py
default=None,
help='Enable the --trace-maps flag in V8 (use at your own risk)')

parser.add_argument('--experimental',
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--experimental is not a great name. wdyt of the following:

Suggested change
parser.add_argument('--experimental',
parser.add_argument('--disable-experimental-flags-gating',

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or --enable-all-experimental rather than disable

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