Ensure that table printer fills the full width of the terminal

mislav · mislav · commit ed15bebb841b · 2021-03-11T19:04:57.000+01:00
Sometimes, due to rounding errors, after calculating the width of each
column in a table, the sum of all columns would be shorter that the
total available width in the terminal. This reimplements the elastic
column resizing algorithm to ensure that all available space has been
filled.

As a bonus fix, columns that contain URLs are never truncated.
diff --git a/pkg/cmd/gist/list/list_test.go b/pkg/cmd/gist/list/list_test.go
@@ -177,7 +177,12 @@ func Test_listRun(t *testing.T) {
 					)),
 				)
 			},
-			wantOut: "1234567890  cool.txt              1 file    public  about 6 hours ago\n4567890123                        1 file    public  about 6 hours ago\n2345678901  tea leaves thwart...  2 files   secret  about 6 hours ago\n3456789012  short desc            11 files  secret  about 6 hours ago\n",
+			wantOut: heredoc.Doc(`
+				1234567890  cool.txt                         1 file    public  about 6 hours ago
+				4567890123                                   1 file    public  about 6 hours ago
+				2345678901  tea leaves thwart those who ...  2 files   secret  about 6 hours ago
+				3456789012  short desc                       11 files  secret  about 6 hours ago
+			`),
 		},
 		{
 			name: "with public filter",
@@ -206,7 +211,10 @@ func Test_listRun(t *testing.T) {
 					)),
 				)
 			},
-			wantOut: "1234567890  cool.txt  1 file  public  about 6 hours ago\n4567890123            1 file  public  about 6 hours ago\n",
+			wantOut: heredoc.Doc(`
+				1234567890  cool.txt  1 file  public  about 6 hours ago
+				4567890123            1 file  public  about 6 hours ago
+			`),
 		},
 		{
 			name: "with secret filter",
@@ -250,7 +258,10 @@ func Test_listRun(t *testing.T) {
 					)),
 				)
 			},
-			wantOut: "2345678901  tea leaves thwart...  2 files   secret  about 6 hours ago\n3456789012  short desc            11 files  secret  about 6 hours ago\n",
+			wantOut: heredoc.Doc(`
+				2345678901  tea leaves thwart those who ...  2 files   secret  about 6 hours ago
+				3456789012  short desc                       11 files  secret  about 6 hours ago
+			`),
 		},
 		{
 			name: "with limit",
diff --git a/utils/table_printer.go b/utils/table_printer.go
@@ -3,6 +3,7 @@ package utils
 import (
 	"fmt"
 	"io"
+	"sort"
 	"strings"
 
 	"github.com/cli/cli/pkg/iostreams"
@@ -34,6 +35,10 @@ type tableField struct {
 	ColorFunc    func(string) string
 }
 
+func (f *tableField) DisplayWidth() int {
+	return text.DisplayWidth(f.Text)
+}
+
 type ttyTablePrinter struct {
 	out      io.Writer
 	maxWidth int
@@ -69,35 +74,9 @@ func (t *ttyTablePrinter) Render() error {
 		return nil
 	}
 
-	numCols := len(t.rows[0])
-	colWidths := make([]int, numCols)
-	// measure maximum content width per column
-	for _, row := range t.rows {
-		for col, field := range row {
-			textLen := text.DisplayWidth(field.Text)
-			if textLen > colWidths[col] {
-				colWidths[col] = textLen
-			}
-		}
-	}
-
 	delim := "  "
-	availWidth := t.maxWidth - colWidths[0] - ((numCols - 1) * len(delim))
-	// add extra space from columns that are already narrower than threshold
-	for col := 1; col < numCols; col++ {
-		availColWidth := availWidth / (numCols - 1)
-		if extra := availColWidth - colWidths[col]; extra > 0 {
-			availWidth += extra
-		}
-	}
-	// cap all but first column to fit available terminal width
-	// TODO: support weighted instead of even redistribution
-	for col := 1; col < numCols; col++ {
-		availColWidth := availWidth / (numCols - 1)
-		if colWidths[col] > availColWidth {
-			colWidths[col] = availColWidth
-		}
-	}
+	numCols := len(t.rows[0])
+	colWidths := t.calculateColumnWidths(len(delim))
 
 	for _, row := range t.rows {
 		for col, field := range row {
@@ -110,7 +89,7 @@ func (t *ttyTablePrinter) Render() error {
 			truncVal := field.TruncateFunc(colWidths[col], field.Text)
 			if col < numCols-1 {
 				// pad value with spaces on the right
-				if padWidth := colWidths[col] - text.DisplayWidth(field.Text); padWidth > 0 {
+				if padWidth := colWidths[col] - field.DisplayWidth(); padWidth > 0 {
 					truncVal += strings.Repeat(" ", padWidth)
 				}
 			}
@@ -132,6 +111,91 @@ func (t *ttyTablePrinter) Render() error {
 	return nil
 }
 
+func (t *ttyTablePrinter) calculateColumnWidths(delimSize int) []int {
+	numCols := len(t.rows[0])
+	allColWidths := make([][]int, numCols)
+	for _, row := range t.rows {
+		for col, field := range row {
+			allColWidths[col] = append(allColWidths[col], field.DisplayWidth())
+		}
+	}
+
+	// calculate max & median content width per column
+	maxColWidths := make([]int, numCols)
+	// medianColWidth := make([]int, numCols)
+	for col := 0; col < numCols; col++ {
+		widths := allColWidths[col]
+		sort.Ints(widths)
+		maxColWidths[col] = widths[len(widths)-1]
+		// medianColWidth[col] = widths[(len(widths)+1)/2]
+	}
+
+	colWidths := make([]int, numCols)
+	// never truncate the first column
+	colWidths[0] = maxColWidths[0]
+	// never truncate the last column if it contains URLs
+	if strings.HasPrefix(t.rows[0][numCols-1].Text, "https://") {
+		colWidths[numCols-1] = maxColWidths[numCols-1]
+	}
+
+	availWidth := func() int {
+		setWidths := 0
+		for col := 0; col < numCols; col++ {
+			setWidths += colWidths[col]
+		}
+		return t.maxWidth - delimSize*(numCols-1) - setWidths
+	}
+	numFixedCols := func() int {
+		fixedCols := 0
+		for col := 0; col < numCols; col++ {
+			if colWidths[col] > 0 {
+				fixedCols++
+			}
+		}
+		return fixedCols
+	}
+
+	// set the widths of short columns
+	if w := availWidth(); w > 0 {
+		if numFlexColumns := numCols - numFixedCols(); numFlexColumns > 0 {
+			perColumn := w / numFlexColumns
+			for col := 0; col < numCols; col++ {
+				if max := maxColWidths[col]; max < perColumn {
+					colWidths[col] = max
+				}
+			}
+		}
+	}
+
+	firstFlexCol := -1
+	// truncate long columns to the remaining available width
+	if numFlexColumns := numCols - numFixedCols(); numFlexColumns > 0 {
+		perColumn := availWidth() / numFlexColumns
+		for col := 0; col < numCols; col++ {
+			if colWidths[col] == 0 {
+				if firstFlexCol == -1 {
+					firstFlexCol = col
+				}
+				if max := maxColWidths[col]; max < perColumn {
+					colWidths[col] = max
+				} else {
+					colWidths[col] = perColumn
+				}
+			}
+		}
+	}
+
+	// add remainder to the first flex column
+	if w := availWidth(); w > 0 && firstFlexCol > -1 {
+		colWidths[firstFlexCol] += w
+		if max := maxColWidths[firstFlexCol]; max < colWidths[firstFlexCol] {
+			colWidths[firstFlexCol] = max
+		}
+	}
+
+	return colWidths
+}
+
 type tsvTablePrinter struct {
 	out        io.Writer
 	currentCol int
