[neilcawse]

What main still gets wrong

Main (84acf62) special-cases plain General in io.rs::csv with Rust's f64::to_string(), and leaves every other General through the 11-character cell display. Saving one row on main gives:

Cell	Format	main writes	this PR writes
0.1+0.2	General	0.30000000000000004	0.3
1/3	General	0.3333333333333333 (16 digits)	0.333333333333333
1/3*1E-6	General	0.0000003333333333333333	0.000000333333333333333
124412140710	[Blue]General	1.24412E+11	124412140710
-124412140710	General;[Red]-General	-1.24412E+11	-124412140710
124412140710	@ (Text)	1.24412E+11	124412140710
124412140710	General" mm"	1.24412E+11 mm	124412140710 mm
1234567890123456, 9007199254740994	General	every digit	every digit (unchanged)
12345678901234567, 1E+20, 1E15-0.5	General	12345678901234568, 100000000000000000000, 999999999999999.5	unchanged

Same for .txt/.tsv. Excel never shows binary noise like 0.30000000000000004: its text conversion (&) stops at 15 significant digits. A CSV export never writes an exponent for a General number, though: reopening the file gives a number typed as 1.23456789012346E+16 a 0.00E+00 format, and the next save writes 1.23E+16. So a number of 1E+15 or more is written as the shortest digits that read back as the same value (every integer below 1e16 that f64 stores is written exactly, so a 16-digit card or order number survives; larger ones as main wrote them, e.g. 12345678901234568, 2^70 as 1180591620717411300000), and a small number as its 15 significant digits in full. A CSV GridCraft wrote, opened and saved again, is unchanged. A CSV from elsewhere can change on its first save: a 16- or 17-digit decimal is cut to 15 digits, as in Excel (3.141592653589793 → 3.14159265358979; main kept it), and a number typed in scientific notation gets the old 0.00E+00 parse format and is saved rounded to it (1.23456789012346E-10 → 1.23E-10, the same on main). Measured with gridcraft-cli convert on 3.141592653589793,0.30000000000000004,1.50,1E+20,1.23456789012346E-10,12345678901234567 (main: 3.141592653589793,0.30000000000000004,1.5,1.00E+20,1.23E-10,12345678901234568; this PR: 3.14159265358979,0.3,1.5,1.00E+20,1.23E-10,12345678901234568; a second save is byte-identical on both).

How this compares with Excel (Excel for Mac 16.114, synthetic sheet, General cells): Excel's own Save As CSV UTF-8 writes General formatting capped at 11 characters per value, so a value that needs more than 11 characters loses digits. It writes 0.333333333 for 1/3, 1.23457E+16 for 12345678901234567 (already cut to 15 digits on entry), 1.15292E+18 for 2^60, 3.14159E+15 for PI()*1E15, 3.33333E-06 for 1E-5/3 and 1E-10. It also writes a UTF-8 BOM and no final line break. This PR writes 0.333333333333333, 12345678901234500, 1152921504606847000, 3141592653589793, 0.00000333333333333333 and 0.0000000001, so it keeps more digits than Excel does, and never writes an exponent. Opened in Excel, the CSVs from this PR (b0c3d8e) and from main (6e984bb) give the same value in all ten cells, because Excel reads 15 significant digits. The one difference is that main's longer text for 0.1+0.2, 1/3 and 1E-5/3 is cut on reading.

Change

• gridcraft_numfmt::format_value_full: like format_value, but a number shown as General (General or Text section, with colour/literals) isn't narrowed to the cell width. It is written by the private general_full: gridcraft_core::number_to_text (the & conversion), unless that text has an exponent; then {} (shortest round trip, main's output) for |n| ≥ 1, or the 15 digits written out for |n| < 1. render_general takes the already-written General text; private format_number gains a full flag (grid callers and the existing numfmt test helper pass false).
• gridcraft_core::number_to_text is not export-only: it is the conversion behind &, CONCAT, TEXTJOIN, VALUETOTEXT, the IM functions' complex text, the formula printer and pivot/chart labels, and all of them change:
  • It rounds to 15 significant digits before choosing decimal or scientific, so =(1E15-0.5)&"" gives 1E+15 (main: 1000000000000000, 16 digits).
  • Below 1, it switches to scientific when the 15-digit decimal would be longer than 21 characters (0. plus 19 decimals; a minus sign is not counted). Excel for Mac cached IMCSCH("13+5j") as 1.28233995888454E-06+4.33496947416312E-06j, IMEXP("-13+25j") as 2.24044486393732E-06-2.99158552811404E-07j, and IMTAN/IMSECH parts as 0.0000692361330972509 / 0.000241377759972715 (the formulas project's test.xlsx in the corpus). So =(9.99999999999999E-9)&"" gives 9.99999999999999E-09 (main: 0.00000001), and =1/3*1E-5&"" gives 3.33333333333333E-06 (main: 0.00000333333333333333). Only 15-digit mantissas are Excel-verified. The boundary for shorter mantissas from 1E-6 to 1E-9 (e.g. 0.0000099999999999999 stays decimal) and the decision to leave the sign out of the count are inferred, not checked against Excel.
  • Below 1E-9 it stays scientific and up to 1E-9 decimal, as before (1E-10, 0.000000001).
• display::value_text (used only by CSV/text export) uses format_value_full; cell_text keeps the cell-width General through a private shown_text, unchanged behaviour.
• io.rs::csv drops its plain-General special case and just calls value_text: one mechanism.
• Tests:
  • delimited_exports_write_general_numbers_as_text_converts_them (CSV and TXT) fails on main with the values above.
  • delimited_exports_preserve_general_precision_and_explicit_number_formats checks 2^53, even integers above it, -9999999999999998, 12345678901234567, 1E+20, 1E15-0.5 and two small numbers, and that reopening and saving the CSV/TSV gives the same bytes.
  • number_text_small_magnitudes (core) checks the Excel-cached values and the cases just below powers of ten (1E-10 to 1E-4, 1E14 to 1E16).
  • text_joins_convert_numbers_to_15_significant_digits (calc) covers &, CONCAT and TEXTJOIN.
  • complex_numbers (functions) checks the Excel-cached IMCSCH, IMEXP and IMSECH text.
• docs/file-format-parity.md: merges the duplicate (contradictory) CSV/text rows and records the intentional difference from Excel, which writes the cell display (1.24412E+11, 0.333333333). docs/function-parity.md records the & conversion change.

The earlier "Fix main CI" commit (French header/footer labels, plain-General CSV) is dropped: main fixed both.

Review

Three adversarial review rounds ran.

Round 1:

• 16+-digit integers no longer lose digits on a CSV open/save. Main wrote them exactly, and the first version rounded them to 15 digits.
• number_to_text rounds to 15 digits before choosing decimal or scientific, so values in [999999999999999.5, 1e15) no longer give a 16-digit integer.

Round 2:

• The 2^53 cutoff for exact integers was wrong: 2^53, the even integers above it and other 16-digit integers are exact in f64, and they came out as 9.00719925474099E+15. CSV export now writes every integer below 1e16 exactly.
• 17+-digit integers keep main's round-trip digits (12345678901234568, 100000000000000000000). No General number is written with an exponent, because reopening the file would give it a scientific format and the next save would round it: 9.00719925474099E+15 became 9.01E+15, and 1.23456789012346E-10 became 1.23E-10, on the build before this round. As a result, 1E15-0.5 exports as 999999999999999.5 again (main's), while & gives 1E+15.
• number_to_text affects every &-style conversion, not only export, and this is now documented. Its small-number switch now matches Excel's cached results (above), not a fixed 1E-9 boundary.
• The stale doc comments in io.rs::csv, format_value_full and value_text are fixed. The "(|x| < 2^53)" wording is gone.

Round 3 (no code bug; wording only):

• The doc comments in io.rs::csv and display::value_text and the file-format-parity header no longer say export writes &'s 15 digits for every General number: from 1E+15 it writes the shortest round-trip digits (999999999999999.5, 12345678901234568). "Every digit" now applies only to integers below 1e16.
• "A CSV opened and saved again is unchanged" is narrowed to files GridCraft wrote, and the changes a foreign CSV gets on its first save are listed (above).
• The 21-character boundaries for mantissas shorter than 15 digits and for negatives are marked as inferred, here and in the number_to_text doc comment, which also says the sign isn't counted.
• The function-parity changelog row gave the wrong "was" value for =(9.99999999999999E-9)&"": it is 0.00000001 on main (measured with gridcraft-cli eval). The row now also marks the inferred boundaries.
• Merge of main f1894c6 (44526f0). Only docs/file-format-parity.md and docs/function-parity.md conflicted (the header line and changelog rows); both sides' rows are kept, newest first, and main's change is listed as "previously" in the header. An adversarial review of the merge against both parents found nothing; it also checked the code that merged without conflicts against main's new formula length and nesting limit (Formula parser: Excel's 8,192-character limit and postfix nesting (never crash) #1330) and the large-range clear recalculation (fix(edit): recalculate all changed cells after large-range clears #1128). cargo xtask ci passes all 8 steps on the merge.
• Merge of main 19f4387 (f410a77). This merge conflicted in crates/engine/src/display.rs with Conditional formatting: show a rule's number format (fixes #1163) #1769, which split value_text_as out of value_text so that print uses the number format of a conditional format. Resolution: value_text (CSV/Text export) keeps this PR's format_value_full, and value_text_as keeps main's cell-display formatting, so print output is the same as on main. shown_text (the cell display) now calls value_text_as. An adversarial review traced every caller (CSV/TSV, print, grid, clipboard, find, remove duplicates) and found nothing. It ran the engine, numfmt and core tests (390 passed), a CSV export of 124412140710 in General (written as 124412140710) and main's conditional_number_format_prints. cargo xtask ci passes all 8 steps on the merge.
• Merge of main c30fa3f (b0c3d8e, Fix MEDIAN overflow for large finite middle values #1585: MEDIAN overflow). Conflicts: docs/function-parity.md (the header line and changelog rows). An adversarial review found nothing; it checked the remerge diff and how the MEDIAN/AGGREGATE midpoint fix interacts with this PR, and ran cargo test -p gridcraft-calc -p gridcraft-functions (186 passed). cargo xtask ci passes all 8 steps on the merge.
• Approved by @FredApps at b0c3d8e (review), from reading the source plus the hosted cargo xtask ci. He covered the CSV/TXT General-number path (number_to_text, format_value_full, display.rs, io.rs) and its tests (12-digit part codes, 2^53, 1e20, 1e15-0.5, reopen and save again); cell_text and print keep the cell-width General. No findings.
• Excel check (Excel for Mac 16.114, synthetic files): the added text had an adversarial review (one finding: Excel's CSV width is a cap, not a fixed width; fixed).
• Merge of main 23829d8 (42d3e9a). Only docs/file-format-parity.md conflicted (its header line and changelog rows): it keeps main's single header line with this PR's change listed first, and both sides' rows. An adversarial review of the merge against both parents found nothing. cargo xtask ci passes all 8 steps on the merged head.
• CodeRabbit on the merged head (comment): the merge of main had dropped main's changelog row for right-to-left text boxes. Restored as on main (3d19fa4); an adversarial review found nothing more. cargo xtask ci passes all 8 steps on 3d19fa4.
• Approved again by @FredApps at 3d19fa4 (review), from re-reading the change against the merge context and the hosted cargo xtask ci run on that head; no local tests.
• Merge of main 06920de (f8c4dac; head 77cfbda). Conflicts: docs/file-format-parity.md and docs/function-parity.md (combined header lines with this PR's entry first; both sides' revision rows). number_to_text in crates/core/src/value.rs merged without a textual conflict but lost main's let a = n.abs(); restored, so this PR's 15-digit General rendering and main's scientific-notation boundary both hold. Adversarial review of the merge against both parents: one finding, revision rows out of date order, fixed in 77cfbda. cargo xtask ci passes all 8 steps on 77cfbda.

Checks

• cargo fmt --all; cargo clippy -p gridcraft-core -p gridcraft-numfmt -p gridcraft-functions -p gridcraft-calc -p gridcraft-engine --all-targets -- -D warnings; cargo test --no-fail-fast for those crates plus gridcraft-formula, gridcraft-xlsx and gridcraft-chart: all pass. Each new regression test fails on the previous head (4dd4ff9).
• Corpus (4,224 files): cd /tmp/gc-corpus2 && .venv/bin/python run.py <release gridcraft-cli> results-449-bf9b3cb, compared per file against results-main-84acf62 (summed totals.mismatched and roundTripDiffering): no file is worse. test__test_files__test.xlsx improves from 1326 to 1321 calc mismatches (the IM text above). Two files hit the 60 s timeout on a machine with load average ~200; rerun with GC_TIMEOUT=600 (results-449-bf9b3cb-retry), they match main (18097 and 0 mismatches). Summed over all files: 68,964 on main, 68,959 here.
• Round 3 (9cbbaae, comments and docs only): cargo fmt --all; cargo test --no-fail-fast -p gridcraft-core -p gridcraft-engine pass. The foreign-CSV and 2^70 outputs quoted above come from gridcraft-cli convert on the release builds of 84acf62 and bf9b3cb.
• cargo xtask ci passes all 8 steps (fmt, clippy, test, assets, layers, wasm, parity, keytips) on the head commit 9cbbaae.

Summary by CodeRabbit

• Bug Fixes
  • Numeric-to-text conversion now uses up to 15 significant digits and selects decimal or scientific notation more consistently for very large and small values.
• Improvements
  • CSV and TSV exports better preserve numeric precision and round-trip stability, including for General-formatted values.
  • Cell display and full-value text output now use distinct formatting behavior.
• Documentation
  • Updated file-format and function-parity documentation to reflect numeric export and conversion behavior.

[neilcawse]

This commit is also included in #417, so merging #417 lands both. You can merge this on its own if you'd rather fix main first.

[neilcawse]

Thanks for testing on the real file. Twenty 12-digit part codes going from 1.24412E+11 back to intact on Windows 11 is the case this PR is meant to fix, and it's good to know the #427 semicolon tests pass with it too.

[FredApps]

Read the whole code diff at b0c3d8e (core number_to_text, numfmt format_value_full/general_full/render_general, engine display.rs and io.rs, the IM function tests, the docs rows). One mechanism now writes General numbers to CSV/TXT: number_to_text's 15 digits below 1E+15, the shortest round-trip digits from there (every integer below 1e16 exact), and never an exponent, so a reopened file does not pick up a scientific format that rounds on the next save. The special case in io.rs that this replaces is covered by the new tests (12-digit part codes, 2^53 and the even integers above it, 1e20, 1e15-0.5), and a reopen-and-save-again equality check is included. cell_text and print keep the cell-width General through shown_text and value_text_as, and TEXT(x,"General") passes full=false, so grid, print and TEXT output are unchanged. The wider effect on number_to_text (&, CONCAT, TEXTJOIN, IM* results) is stated in the PR, with the small-magnitude cases checked against Excel-cached IM results and unit tests for each boundary. I traced the rounding-first step for 999999999999999.5, 9.999999999999999e-10 and 9.999999999999999e-6 and the results match the asserted ones.

The thread has a real-file confirmation on Windows (twenty 12-digit part codes written back intact).

Validation: source reading plus the hosted cargo xtask ci check, green at b0c3d8e on a clean merge with main. No local tests were run (builds are paused).

[coderabbitai]

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Reviewing files that changed from the base of the PR and between 77cfbda and c0bc784.

Files selected for processing: 4

• crates/calc/src/tests.rs
• crates/engine/src/io.rs
• crates/functions/src/engineering.rs
• docs/function-parity.md

Files skipped from review as they are similar to previous changes: 1

• docs/function-parity.md

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Walkthrough

The change updates number-to-text rounding and notation rules, adds full-width General formatting, and routes CSV/TSV cell output through that path. Tests cover number conversion, formatting, and export round trips. Parity documents describe the formatting behavior.

Changes: Numeric text formatting and export

Layer / File(s)	Summary
Number-to-text rounding and notation crates/core/src/value.rs, crates/calc/src/tests.rs, crates/functions/src/engineering.rs, docs/function-parity.md	number_to_text uses rounded 15-significant-digit values to select decimal or scientific notation. Tests cover boundary values, concatenation functions, and complex-number output.
Full-width General formatting crates/numfmt/src/lib.rs, crates/numfmt/src/render.rs, crates/numfmt/src/tests.rs	The formatter adds a full-width General path and passes preformatted text to the General renderer. TEXT() continues to use width-limited formatting.
Delimited export integration crates/engine/src/display.rs, crates/engine/src/io.rs, docs/file-format-parity.md	Display formatting separates cell-width output from full-width value output. CSV/TSV export uses full-width value text. Tests cover formatted values and export round trips.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Export as CSV/TSV export
  participant Display as display::value_text
  participant Formatter as format_value_full
  participant NumberFormat
  Export->>Display: Format each cell
  Display->>Formatter: Format value
  Formatter->>NumberFormat: Apply full-width General formatting
  NumberFormat-->>Display: Return formatted text
  Display-->>Export: Return cell text

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Possibly related issues

• storytold/gridcraft#506 — The PR preserves exact integer digits in General CSV export, addressing the reported saved-file conversion of ID codes to scientific form.

Possibly related PRs

• storytold/gridcraft#2559 — Changes text-file and delimited-file numeric export in the same I/O path.
• storytold/gridcraft#2289 — Uses number_to_text when printing formula numbers, so its output relies on the conversion rules changed here.
• storytold/gridcraft#2466 — Changes CSV/TXT numeric export and overlaps with this PR’s General-number output contract.

Suggested reviewers: dylanmtaylor, echelon

Merge Risk: Minimal · up to c0bc7

No confirmed formatting or export issue remains to block merging after normal checks.

Architecture risk: Low · up to c0bc7

The change affects 2 systems.

Changed systems: crates, docs

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — crates (service) was modified; 8 changed files map to changed impact.
• observed — docs (service) was modified; 2 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in crates/numfmt/src/render.rs: Removed the unused format_general_fit import from the decimal helpers.
• observed — Modified behavior in crates/numfmt/src/render.rs: render_general now receives preformatted general text and emits it directly for Tok::General; the previous numeric formatting, width constraint, and # fallback were removed.
• observed — Modified behavior in crates/core/src/value.rs: number_to_text now documents and applies decimal/scientific selection using the rounded 15-digit mantissa: scientific notation is used outside exponents -9 through 14, for sub-unit values needing over 19 decimal places, and when rounding reaches 1E+15. This replaces the prior magnitude check, which used a.round() for small values and selected notation based on magnitude rather than decimal length.
• observed — Modified behavior in crates/core/src/value.rs: The number_text expectations now include signed values just below 1E+15, rounding near 1E-9, and decimal output for rounded values below the scientific threshold. A new number_text_small_magnitudes test checks decimal-length boundaries, positive and negative small-number formatting, and large-number formatting around 1E+15.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly describes the two primary changes: General-number CSV/text export without exponents and scientific notation for ampersand conversion beyond 21 characters. It is specific and related …
Docstring Coverage		Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 30 functions across 8 files. (1 skipped: 1 …
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title clearly describes the two primary changes: General-number CSV/text export without exponents and scientific notation for ampersand conversion beyond 21 characters. It is specific and related to the changeset, although somewhat long.

Full details: Docstring Coverage

Explanation

Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 30 functions across 8 files. (1 skipped: 1 unsupported.)

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Inline comments:
Review comments at @docs/file-format-parity.md:
- Line 88: Add the missing 2026-10-19 minor revision row for XLSX text boxes and
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📥 Commits

Reviewing files that changed from the base of the PR and between 23829d8 and 42d3e9a.

📒 Files selected for processing: 10

• crates/calc/src/tests.rs
• crates/core/src/value.rs
• crates/engine/src/display.rs
• crates/engine/src/io.rs
• crates/functions/src/engineering.rs
• crates/numfmt/src/lib.rs
• crates/numfmt/src/render.rs
• crates/numfmt/src/tests.rs
• docs/file-format-parity.md
• docs/function-parity.md

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[FredApps]

Re-reviewed 3d19fa4: the current CSV/TXT General-number export changes and merge-context adjustments preserve the previously reviewed behavior and regressions. Verified exact-head hosted cargo xtask ci run 39366072369. No local tests were run.