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timezone info unavailable in builds with small ICU

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
javascript, nodejs
Domain
build-system, internationalization

Research direction

Reproduce the failure with the provided nix-shell command using small ICU and Temporal, then trace Temporal.Instant.toString() through the timezone-info loading path. Inspect how ICU computes the length of the final Zoneinfo64 item. Done means the command completes without the timezone error and the assertion produces the expected string.

Written by the indexing model from the issue text.

Description

Version

main

Platform
Subsystem

No response

What steps will reproduce the bug?
nix-shell --argstr icu small --arg withTemporal true --arg devTools '[]' --arg benchmarkTools '[]' --run 'make build-ci -j8'
./node -e 'assert.strictEqual(Temporal.Instant.from("1969-07-20T20:17:00Z").toString(), "1969-07-20T20:17:00Z")'
How often does it reproduce? Is there a required condition?

small ICU with Temporal

What is the expected behavior? Why is that the expected behavior?

Temporal.Instant.from("1969-07-20T20:17:00Z").toString() should output the input string

What do you see instead?
assert.strictEqual(Temporal.Instant.from("1969-07-20T20:17:00Z").toString(), "1969-07-20T20:17:00Z")
                                                                 ^

Error: Temporal error: Internal error: Failed to load timezone info.
    at Instant.toString (<anonymous>)
    at [eval]:1:66
    at runScriptInThisContext (node:internal/vm:219:10)
    at node:internal/process/execution:485:12
    at [eval]-wrapper:6:24
    at runScriptInContext (node:internal/process/execution:483:60)
    at evalFunction (node:internal/process/execution:317:30)
    at evalTypeScript (node:internal/process/execution:329:3)
    at node:internal/main/eval_string:71:3

Node.js v27.0.0-pre
Additional information

Refs: https://github.com/nodejs/node/issues/62676

According to @srl295, this is due to how ICU compute length: it compares the position of the item and the position of the next item; in this case, Zoneinfo64 is the last item, so there are no "next item" to compute the length so it assumes it's empty and throws.

Dominant language
JavaScript
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Merged PRs (30d)
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