dualfroz
dc9063405a
SetRows stored rows with fewer cells than the header unchanged, so short rows rendered fmt's %!s(MISSING) verb and an empty row combined with a first-column formatter panicked on vals[0]. Pad short rows to the column count, mirroring AddRow's documented behavior of rendering missing cells as empty.
84 lines
2.5 KiB
Markdown
84 lines
2.5 KiB
Markdown
# fix: pad short rows in SetRows to the number of columns
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## Problem
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`SetRows` does not pad rows that have fewer cells than the table has columns.
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As a result, short rows render fmt's missing-argument verb, and an empty row
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combined with a first-column formatter panics:
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```go
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tbl := table.New("A", "B", "C").WithPadding(1)
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tbl.SetRows([][]string{{"x", "y"}})
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tbl.Print()
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// A B C
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// x y %!s(MISSING)
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```
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```go
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tbl := table.New("A", "B").
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WithFirstColumnFormatter(func(f string, v ...interface{}) string { return fmt.Sprintf(f, v...) })
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tbl.SetRows([][]string{{}})
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tbl.Print() // panic: runtime error: index out of range [0] with length 0
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```
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`AddRow` already handles this: it allocates `make([]string, len(t.header))` per
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row, so short input renders the remaining columns empty. The documented
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behaviour ("Rows can have less cells than the total number of columns;
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subsequent cells will be rendered empty.") is not honored by `SetRows`.
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## Root cause
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`table.go`, `SetRows`:
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```go
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for _, row := range rows {
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if len(row) > headerLength {
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t.rows = append(t.rows, row[:headerLength])
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} else {
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t.rows = append(t.rows, row) // short rows stored as-is
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}
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}
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```
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Short rows are stored unchanged. Later, `printRow` builds one value per cell of
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the row and passes them to `fmt.Fprintf` with a format string containing
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`len(t.header)` verbs, so missing cells become `%!s(MISSING)`. With a
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first-column formatter, `printRow` also indexes `vals[0]`, which panics for an
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empty row.
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## Fix
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Pad short rows to the number of columns, mirroring `AddRow`:
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```go
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switch {
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case len(row) > headerLength:
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t.rows = append(t.rows, row[:headerLength])
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case len(row) < headerLength:
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// pad short rows so every column is rendered, matching AddRow
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padded := make([]string, headerLength)
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copy(padded, row)
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t.rows = append(t.rows, padded)
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default:
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t.rows = append(t.rows, row)
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}
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```
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## Test
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Added `TestSetRowsShortRowsPadded` (asserts no `MISSING` verb and the exact
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padded output) and `TestSetRowsEmptyRowWithFirstColumnFormatter` (asserts no
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panic).
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- Gate (`GOTOOLCHAIN=go1.25.10`): `go test ./...` -> ok (PASS, exit 0)
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- `go vet ./...` -> exit 0
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- `go build ./...` -> exit 0
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Counterfactual: reverting `SetRows` makes `TestSetRowsShortRowsPadded` fail with
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`output contains missing-arg verb: "A B C \nx y %!s(MISSING)\n"`.
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Note: `gofmt -l table.go` reports the file, but this is pre-existing (the
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`Print()` block near line 258 is space-indented on the base commit) and
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unrelated to this change; the modified region is gofmt-clean, so unrelated lines
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were intentionally left untouched.
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