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Trim an oversized device report's comment by bytes - #41
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fitted dropped one unicode scalar per byte over the limit. An emoji is four bytes, so it threw away up to four times what it had to, and when the excess passed the scalar count the whole comment went (2000 emoji fitted to 4000 bytes came back with no comment at all). Keep the longest prefix of whole characters whose UTF-8 size fits instead, so a multi-scalar emoji is never left half built. The loop still re-checks for JSON escaping.
Device and crash reports had the same comment-trimming loop. It now lives in `ReportComment.trimmed`, used by both. It also measures each character as the report's encoder writes it, so a comment full of quotes, backslashes, slashes or newlines (two bytes each in the JSON) is cut by what it really costs. Before, those were counted at one byte and twice as much was cut as needed. Only characters JSON may escape go through the encoder; the rest count as their UTF-8 size, which keeps it cheap for the windows that fit the report on every keystroke. One pass now always fits; the loop is only a guard.
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What
DeviceReportOutput.fittedcut the comment withunicodeScalars.dropLast(excess), whereexcessis a byte count. An emoji is four bytes, so it dropped up to four times what it had to. When the excess was bigger than the number of scalars, the comment was lost entirely. For example, 2000 emoji fitted to 4000 bytes came back with no comment.Now device and crash reports share one trim,
ReportComment.trimmed:fittedis only a guard.Tests
ReportCommentTests: emoji cut by their bytes, escaped characters at their JSON size, whole characters only, nothing left is nil.swift test: 344 tests, 0 failures. No warnings.