Add CreateFormatterObject AO by jessealama · Pull Request #94 · tc39/proposal-amount

jessealama · 2026-04-01T10:09:43Z

Adds the CreateFormatterObject abstract operation, which builds the formatter object (with internal slots for rounding mode, digit limits, etc.) needed by FormatNumericToString. Replaces the TODO placeholders in the Amount constructor and convertTo with actual calls to this new AO. Spun off from #89 per reviewer feedback. Closes #93.

Replace TODO placeholders in the Amount constructor and convertTo with actual CreateFormatterObject calls that build the formatter object needed by FormatNumericToString. Closes #93

github-actions · 2026-04-01T10:10:11Z

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gibson042

This is a change for the better, but is not currently addressing #89 (comment) .

spec.emu

Co-authored-by: Richard Gibson <richard.gibson@gmail.com>

gibson042

This looks good after fixing the typing to correctly map integral Numbers to integers where required.

And for a potential followup, there's a common pattern here that has me wondering whether a new operation is warranted:

  1. If _x_ is not *undefined*, set _x_ to ? SnapToInteger(_x_, ~strict~, 1, 21).

where the second parameter is either ~strict~ to reject non-integral output from ToNumber or ~truncate-strict~ to reject non-finite output but truncate finite non-integers, and the optional third and fourth parameters respectively define inclusive lower and upper bounds.

Such an operation could replace Temporal ToIntegerIfIntegral(x) with SnapToInteger(x, ~strict~), Temporal ToIntegerWithTruncation(x) with SnapToInteger(x, ~truncate-strict~), and Temporal ToPositiveIntegerWithTruncation(x) with SnapToInteger(x, ~truncate-strict~, 1). It could potentially even be extended to consolidate almost all integer conversions by introducing a ~truncate-loose~ behavior (truncating finite non-integer output from ToNumber and mapping NaN to 0) for use in the definition of ToLength and ToIndex (respectively, 𝔽(the result of clamping SnapToInteger(argument, ~truncate-loose~) between 0 and 2⁵³ - 1) and SnapToInteger(argument, ~truncate-loose~, 0, 2⁵³ - 1)):

Operation	NaN	±∞	Finite non-integer	Bounds	Behavior
ToIntegerOrInfinity	→ 0	preserve	truncate		n/a
ToIntegerIfIntegral (Temporal)	RangeError	RangeError	RangeError		STRICT
ToIntegerWithTruncation (Temporal)	RangeError	RangeError	truncate		TRUNCATE-STRICT
ToPositiveIntegerWithTruncation (Temporal)	RangeError	RangeError	truncate	RangeError if ≤ 0	TRUNCATE-STRICT
ToLength	→ 0	preserve	truncate	clamp to [0, 2**53 - 1]	TRUNCATE-LOOSE
ToIndex	→ 0	preserve	truncate	RangeError if outside [0, 2**53 - 1]	TRUNCATE-LOOSE
DefaultNumberOption (ECMA-402)	RangeError	RangeError	preserve	RangeError if outside [min, max]¹	n/a¹
GetAmountOptions	RangeError	RangeError	RangeError	RangeError if outside [min, max]	STRICT
GetAmountConvertToOptions	RangeError	RangeError	RangeError	RangeError if outside [min, max]	STRICT

DefaultNumberOption currently checks output from ToNumber against specified bounds before truncation: https://github.com/tc39/ecma402/issues/691 ↩ ↩²

gibson042 · 2026-04-02T15:40:48Z

spec.emu

            1. If _fractionDigits_ is not an integral Number, throw a *RangeError* exception.
+            1. If _fractionDigits_ &lt; *-0*<sub>𝔽</sub> or _fractionDigits_ > *100*<sub>𝔽</sub>, throw a *RangeError* exception.


The operation header requires [[FractionDigits]] to be undefined or an integer, so let's convert it here and remove the awkward use of -0_𝔽.

Suggested change

1. If _fractionDigits_ is not an integral Number, throw a *RangeError* exception.

1. If _fractionDigits_ < *-0*𝔽 or _fractionDigits_ > *100*𝔽, throw a *RangeError* exception.

1. If _fractionDigits_ is not an integral Number, throw a *RangeError* exception.

1. Set _fractionDigits_ to ℝ(_fractionDigits_).

1. If _fractionDigits_ is not in the inclusive interval from 0 to 100, throw a *RangeError* exception.

gibson042 · 2026-04-02T15:46:02Z

spec.emu

            1. If _significantDigits_ is not an integral Number, throw a *RangeError* exception.
-            1. If _significantDigits_ &lt; *1*<sub>𝔽</sub>, throw a *RangeError* exception.
+            1. If _significantDigits_ &lt; *1*<sub>𝔽</sub> or _significantDigits_ > *21*<sub>𝔽</sub>, throw a *RangeError* exception.


Suggested change

1. If _significantDigits_ is not an integral Number, throw a *RangeError* exception.

1. If _significantDigits_ < *1*𝔽, throw a *RangeError* exception.

1. If _significantDigits_ < *1*𝔽 or _significantDigits_ > *21*𝔽, throw a *RangeError* exception.

1. If _significantDigits_ is not an integral Number, throw a *RangeError* exception.

1. Set _significantDigits_ to ℝ(_significantDigits_).

1. If _significantDigits_ is not in the inclusive interval from 1 to 21, throw a *RangeError* exception.

gibson042 · 2026-04-02T16:02:28Z

spec.emu

+          1. If _minFractionDigits_ is not *undefined*, then
+            1. If _minFractionDigits_ is not an integral Number, or _minFractionDigits_ &lt; *-0*<sub>𝔽</sub>, or _minFractionDigits_ > *100*<sub>𝔽</sub>, throw a *RangeError* exception.
+          1. If _maxFractionDigits_ is not *undefined*, then
+            1. If _maxFractionDigits_ is not an integral Number, or _maxFractionDigits_ &lt; *-0*<sub>𝔽</sub>, or _maxFractionDigits_ > *100*<sub>𝔽</sub>, throw a *RangeError* exception.


Suggested change

1. If _minFractionDigits_ is not *undefined*, then

1. If _minFractionDigits_ is not an integral Number, or _minFractionDigits_ < *-0*𝔽, or _minFractionDigits_ > *100*𝔽, throw a *RangeError* exception.

1. If _maxFractionDigits_ is not *undefined*, then

1. If _maxFractionDigits_ is not an integral Number, or _maxFractionDigits_ < *-0*𝔽, or _maxFractionDigits_ > *100*𝔽, throw a *RangeError* exception.

1. If _minFractionDigits_ is not *undefined*, then

1. If _minFractionDigits_ is not an integral Number, throw a *RangeError* exception.

1. Set _minFractionDigits_ to ℝ(_minFractionDigits_).

1. If _minFractionDigits_ is not in the inclusive interval from 0 to 100, throw a *RangeError* exception.

1. If _maxFractionDigits_ is not *undefined*, then

1. If _maxFractionDigits_ is not an integral Number, throw a *RangeError* exception.

1. Set _maxFractionDigits_ to ℝ(_maxFractionDigits_).

1. If _maxFractionDigits_ is not in the inclusive interval from 0 to 100, throw a *RangeError* exception.

gibson042 · 2026-04-02T17:43:34Z

spec.emu

+          1. If _minSignificantDigits_ is not *undefined*, then
+            1. If _minSignificantDigits_ is not an integral Number, or _minSignificantDigits_ &lt; *1*<sub>𝔽</sub>, or _minSignificantDigits_ > *21*<sub>𝔽</sub>, throw a *RangeError* exception.
+          1. If _maxSignificantDigits_ is not *undefined*, then
+            1. If _maxSignificantDigits_ is not an integral Number, or _maxSignificantDigits_ &lt; *1*<sub>𝔽</sub>, or _maxSignificantDigits_ > *21*<sub>𝔽</sub>, throw a *RangeError* exception.


Suggested change

1. If _minSignificantDigits_ is not *undefined*, then

1. If _minSignificantDigits_ is not an integral Number, or _minSignificantDigits_ < *1*𝔽, or _minSignificantDigits_ > *21*𝔽, throw a *RangeError* exception.

1. If _maxSignificantDigits_ is not *undefined*, then

1. If _maxSignificantDigits_ is not an integral Number, or _maxSignificantDigits_ < *1*𝔽, or _maxSignificantDigits_ > *21*𝔽, throw a *RangeError* exception.

1. If _minSignificantDigits_ is not *undefined*, then

1. If _minSignificantDigits_ is not an integral Number, throw a *RangeError* exception.

1. Set _minSignificantDigits_ to ℝ(_minSignificantDigits_).

1. If _minSignificantDigits_ is not in the inclusive interval from 1 to 21, throw a *RangeError* exception.

1. If _maxSignificantDigits_ is not *undefined*, then

1. If _maxSignificantDigits_ is not an integral Number, throw a *RangeError* exception.

1. Set _maxSignificantDigits_ to ℝ(_maxSignificantDigits_).

1. If _maxSignificantDigits_ is not in the inclusive interval from 1 to 21, throw a *RangeError* exception.

Add CreateFormatterObject AO and wire up FormatNumericToString calls

db9b04b

Replace TODO placeholders in the Amount constructor and convertTo with actual CreateFormatterObject calls that build the formatter object needed by FormatNumericToString. Closes #93

gibson042 reviewed Apr 1, 2026

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jessealama and others added 3 commits April 2, 2026 15:28

Update spec.emu

795bfdd

Co-authored-by: Richard Gibson <richard.gibson@gmail.com>

Ensure significant and fractional digits are in range

1ffaa32

intl: Pass along significant/fraction digits to new formatter AO

7f2bad0

gibson042 reviewed Apr 2, 2026

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gibson042 mentioned this pull request Apr 2, 2026

Normative: add Temporal tc39/ecma262#3759

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Add CreateFormatterObject AO#94

Add CreateFormatterObject AO#94
jessealama wants to merge 4 commits intomainfrom
create-formatter-object

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		1. If _fractionDigits_ is not an integral Number, throw a RangeError exception.
		1. If _fractionDigits_ < -0<sub>𝔽</sub> or _fractionDigits_ > 100<sub>𝔽</sub>, throw a RangeError exception.

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