mbeckerle commented on code in PR #1138:
URL: https://github.com/apache/daffodil/pull/1138#discussion_r1447669854
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daffodil-runtime1/src/main/scala/org/apache/daffodil/runtime1/processors/EvTextNumber.scala:
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@@ -186,6 +186,31 @@ class TextNumberFormatEv(
}
}
+ // If textNumberPattern specifies a pad character before the number
pattern and without a
+ // positive prefix, then ICU defaults to a pad position of
PAD_BEFORE_PREFIX with no way to
+ // change it with just the pattern. This is reasonable for most cases,
like when the pad
+ // character is a space. However, if the pad character in
textNumberPattern is '0', then
+ // negative numbers are padded with a '0' before the negative sign. For
example, a pattern
+ // of "*0####0" unparses -123 to "0-123". This is very unlikely to be what
the user wants
+ // with this pattern.
+ //
+ // So in this very specific case, we change the pad position to
PAD_AFTER_PREFIX so the zero
+ // pad character appears after the negative sign, e.g. "-0123". Note that
the check for
+ // format width > 0 is used to test if padding is enabled at all--there is
no specific API
+ // for this, and this is how ICU determines to add padding or not.
+ //
+ // If a user really wants '0' characters to the left of the negative sign,
they can use
+ // textPadKind/textTrimKind and textNumberPadCharacter to uses Daffodils
padding logic
+ // instead of ICUs.
+ if (
Review Comment:
Yeah, I think we'd have to play a similar game on parsing, split the pattern
into two parts as previously described, parse the data with the negative
pattern (using it as a positive pattern) and if that succeeds use that negative
pattern result (but negate it), otherwise use the positive pattern parse
result.
That would address the concern of what if the positive and negative patterns
are very different, and be symmetric in behavior between parse and unparse.
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