New feature: Highlighting whitespace errors

README.md

@@ -68,6 +68,7 @@ You can also check out the website for Micro at https://micro-editor.github.io.
 - Small and simple.
 - Easily configurable.
 - Macros.
+- Smart highlighting of trailing whitespace and tab vs space errors.
 - Common editor features such as undo/redo, line numbers, Unicode support, soft wrapping, …
 
 ## Installation

internal/action/bufpane.go

@@ -509,6 +509,14 @@ func (h *BufPane) HandleEvent(event tcell.Event) {
 			InfoBar.ClearGutter()
 		}
 	}
+
+	cursors := h.Buf.GetCursors()
+	for _, c := range cursors {
+		if c.NewTrailingWsY != c.Y && (!c.HasSelection() ||
+			(c.NewTrailingWsY != c.CurSelection[0].Y && c.NewTrailingWsY != c.CurSelection[1].Y)) {
+			c.NewTrailingWsY = -1
+		}
+	}
 }
 
 // Bindings returns the current bindings tree for this buffer.

internal/buffer/cursor.go

@@ -30,6 +30,11 @@ type Cursor struct {
 	// to know what the original selection was
 	OrigSelection [2]Loc
 
+	// The line number where a new trailing whitespace has been added
+	// or -1 if there is no new trailing whitespace at this cursor.
+	// This is used for checking if a trailing whitespace should be highlighted
+	NewTrailingWsY int
+
 	// Which cursor index is this (for multiple cursors)
 	Num int
 }
@@ -38,6 +43,8 @@ func NewCursor(b *Buffer, l Loc) *Cursor {
 	c := &Cursor{
 		buf: b,
 		Loc: l,
+
+		NewTrailingWsY: -1,
 	}
 	c.StoreVisualX()
 	return c

internal/buffer/eventhandler.go

@@ -106,6 +106,10 @@ func (eh *EventHandler) DoTextEvent(t *TextEvent, useUndo bool) {
 		c.Relocate()
 		c.LastVisualX = c.GetVisualX()
 	}
+
+	if useUndo {
+		eh.updateTrailingWs(t)
+	}
 }
 
 // ExecuteTextEvent runs a text event
@@ -290,6 +294,7 @@ func (eh *EventHandler) UndoOneEvent() {
 	if teCursor.Num >= 0 && teCursor.Num < len(eh.cursors) {
 		t.C = *eh.cursors[teCursor.Num]
 		eh.cursors[teCursor.Num].Goto(teCursor)
+		eh.cursors[teCursor.Num].NewTrailingWsY = teCursor.NewTrailingWsY
 	} else {
 		teCursor.Num = -1
 	}
@@ -333,6 +338,7 @@ func (eh *EventHandler) RedoOneEvent() {
 	if teCursor.Num >= 0 && teCursor.Num < len(eh.cursors) {
 		t.C = *eh.cursors[teCursor.Num]
 		eh.cursors[teCursor.Num].Goto(teCursor)
+		eh.cursors[teCursor.Num].NewTrailingWsY = teCursor.NewTrailingWsY
 	} else {
 		teCursor.Num = -1
 	}
@@ -342,3 +348,58 @@ func (eh *EventHandler) RedoOneEvent() {
 
 	eh.UndoStack.Push(t)
 }
+
+// updateTrailingWs updates the cursor's trailing whitespace status after a text event
+func (eh *EventHandler) updateTrailingWs(t *TextEvent) {
+	if len(t.Deltas) != 1 {
+		return
+	}
+	text := t.Deltas[0].Text
+	start := t.Deltas[0].Start
+	end := t.Deltas[0].End
+
+	c := eh.cursors[eh.active]
+	isEol := func(loc Loc) bool {
+		return loc.X == util.CharacterCount(eh.buf.LineBytes(loc.Y))
+	}
+	if t.EventType == TextEventInsert && c.Loc == end && isEol(end) {
+		var addedTrailingWs bool
+		addedAfterWs := false
+		addedWsOnly := false
+		if start.Y == end.Y {
+			addedTrailingWs = util.HasTrailingWhitespace(text)
+			addedWsOnly = util.IsBytesWhitespace(text)
+			addedAfterWs = start.X > 0 && util.IsWhitespace(c.buf.RuneAt(Loc{start.X - 1, start.Y}))
+		} else {
+			lastnl := bytes.LastIndex(text, []byte{'\n'})
+			addedTrailingWs = util.HasTrailingWhitespace(text[lastnl+1:])
+		}
+
+		if addedTrailingWs && !(addedAfterWs && addedWsOnly) {
+			c.NewTrailingWsY = c.Y
+		} else if !addedTrailingWs {
+			c.NewTrailingWsY = -1
+		}
+	} else if t.EventType == TextEventRemove && c.Loc == start && isEol(start) {
+		removedAfterWs := util.HasTrailingWhitespace(eh.buf.LineBytes(start.Y))
+		var removedWsOnly bool
+		if start.Y == end.Y {
+			removedWsOnly = util.IsBytesWhitespace(text)
+		} else {
+			firstnl := bytes.Index(text, []byte{'\n'})
+			removedWsOnly = util.IsBytesWhitespace(text[:firstnl])
+		}
+
+		if removedAfterWs && !removedWsOnly {
+			c.NewTrailingWsY = c.Y
+		} else if !removedAfterWs {
+			c.NewTrailingWsY = -1
+		}
+	} else if c.NewTrailingWsY != -1 && start.Y != end.Y && c.Loc.GreaterThan(start) &&
+		((t.EventType == TextEventInsert && c.Y == c.NewTrailingWsY+(end.Y-start.Y)) ||
+			(t.EventType == TextEventRemove && c.Y == c.NewTrailingWsY-(end.Y-start.Y))) {
+		// The cursor still has its new trailingws
+		// but its line number was shifted by insert or remove of lines above
+		c.NewTrailingWsY = c.Y
+	}
+}

internal/config/settings.go

@@ -289,6 +289,8 @@ var defaultCommonSettings = map[string]interface{}{
 	"fileformat":      defaultFileFormat(),
 	"filetype":        "unknown",
 	"hlsearch":        false,
+	"hltaberrors":     false,
+	"hltrailingws":    false,
 	"incsearch":       true,
 	"ignorecase":      true,
 	"indentchar":      " ",

internal/display/bufwindow.go

@@ -495,6 +495,12 @@ func (w *BufWindow) displayBuffer() {
 			vloc.X = w.gutterOffset
 		}
 
+		bline := b.LineBytes(bloc.Y)
+		blineLen := util.CharacterCount(bline)
+
+		leadingwsEnd := len(util.GetLeadingWhitespace(bline))
+		trailingwsStart := blineLen - util.CharacterCount(util.GetTrailingWhitespace(bline))
+
 		line, nColsBeforeStart, bslice, startStyle := w.getStartInfo(w.StartCol, bloc.Y)
 		if startStyle != nil {
 			curStyle = *startStyle
@@ -518,6 +524,37 @@ func (w *BufWindow) displayBuffer() {
 					// over cursor-line and color-column
 					dontOverrideBackground := origBg != defBg
 
+					if b.Settings["hltaberrors"].(bool) {
+						if s, ok := config.Colorscheme["tab-error"]; ok {
+							isTab := (r == '\t') || (r == ' ' && !showcursor)
+							if (b.Settings["tabstospaces"].(bool) && isTab) ||
+								(!b.Settings["tabstospaces"].(bool) && bloc.X < leadingwsEnd && r == ' ' && !isTab) {
+								fg, _, _ := s.Decompose()
+								style = style.Background(fg)
+								dontOverrideBackground = true
+							}
+						}
+					}
+
+					if b.Settings["hltrailingws"].(bool) {
+						if s, ok := config.Colorscheme["trailingws"]; ok {
+							if bloc.X >= trailingwsStart && bloc.X < blineLen {
+								hl := true
+								for _, c := range cursors {
+									if c.NewTrailingWsY == bloc.Y {
+										hl = false
+										break
+									}
+								}
+								if hl {
+									fg, _, _ := s.Decompose()
+									style = style.Background(fg)
+									dontOverrideBackground = true
+								}
+							}
+						}
+					}
+
 					for _, c := range cursors {
 						if c.HasSelection() &&
 							(bloc.GreaterEqual(c.CurSelection[0]) && bloc.LessThan(c.CurSelection[1]) ||

internal/util/util.go

@@ -16,6 +16,7 @@ import (
 	"strings"
 	"time"
 	"unicode"
+	"unicode/utf8"
 
 	"github.com/blang/semver"
 	runewidth "github.com/mattn/go-runewidth"
@@ -363,6 +364,28 @@ func GetLeadingWhitespace(b []byte) []byte {
 	return ws
 }
 
+// GetTrailingWhitespace returns the trailing whitespace of the given byte array
+func GetTrailingWhitespace(b []byte) []byte {
+	ws := []byte{}
+	for len(b) > 0 {
+		r, size := utf8.DecodeLastRune(b)
+		if IsWhitespace(r) {
+			ws = append([]byte(string(r)), ws...)
+		} else {
+			break
+		}
+
+		b = b[:len(b)-size]
+	}
+	return ws
+}
+
+// HasTrailingWhitespace returns true if the given byte array ends with a whitespace
+func HasTrailingWhitespace(b []byte) bool {
+	r, _ := utf8.DecodeLastRune(b)
+	return IsWhitespace(r)
+}
+
 // IntOpt turns a float64 setting to an int
 func IntOpt(opt interface{}) int {
 	return int(opt.(float64))

runtime/colorschemes/atom-dark.micro

@@ -29,3 +29,5 @@ color-link color-column "#2D2F31"
 #color-link type.extended "default"
 #Plain brackets
 color-link match-brace "#1D1F21,#62B1FE"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/bubblegum.micro

@@ -27,3 +27,5 @@ color-link color-column "254"
 color-link type.extended "241,231"
 color-link symbol.brackets "241,231"
 color-link match-brace "231,28"
+color-link tab-error "210"
+color-link trailingws "210"

runtime/colorschemes/cmc-16.micro

@@ -43,3 +43,5 @@ color-link color-column "cyan"
 color-link underlined.url "underline blue, white"
 color-link divider "blue"
 color-link match-brace "black,cyan"
+color-link tab-error "brightred"
+color-link trailingws "brightred"

runtime/colorschemes/cmc-tc.micro

@@ -39,3 +39,5 @@ color-link constant.bool "bold #55ffff"
 color-link constant.bool.true "bold #85ff85"
 color-link constant.bool.false "bold #ff8585"
 color-link match-brace "#1e2124,#55ffff"
+color-link tab-error "#d75f5f"
+color-link trailingws "#d75f5f"

runtime/colorschemes/darcula.micro

@@ -30,3 +30,5 @@ color-link type.extended "default"
 #color-link symbol.brackets "default"
 color-link symbol.tag "#AE81FF,#242424"
 color-link match-brace "#242424,#7A9EC2"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/default.micro

@@ -30,3 +30,5 @@ color-link type.extended "default"
 #color-link symbol.brackets "default"
 color-link symbol.tag "#AE81FF,#282828"
 color-link match-brace "#282828,#AE81FF"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/dracula-tc.micro

@@ -44,3 +44,6 @@ color-link color-column "#44475A"
 color-link type.extended "default"
 
 color-link match-brace "#282A36,#FF79C6"
+
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/dukedark-tc.micro

@@ -34,3 +34,5 @@ color-link type.keyword "bold #5aaae6,#001e28"
 color-link type.extended "#ffffff,#001e28"
 color-link underlined "#608b4e,#001e28"
 color-link match-brace "#001e28,#5aaae6"
+color-link tab-error "#d75f5f"
+color-link trailingws "#d75f5f"

runtime/colorschemes/dukelight-tc.micro

@@ -34,3 +34,5 @@ color-link type.keyword "bold #780050,#f0f0f0"
 color-link type.extended "#000000,#f0f0f0"
 color-link underlined "#3f7f5f,#f0f0f0"
 color-link match-brace "#f0f0f0,#780050"
+color-link tab-error "#ff8787"
+color-link trailingws "#ff8787"

runtime/colorschemes/dukeubuntu-tc.micro

@@ -34,3 +34,5 @@ color-link type.keyword "bold #5aaae6,#2d0023"
 color-link type.extended "#ffffff,#2d0023"
 color-link underlined "#886484,#2d0023"
 color-link match-brace "#2d0023,#5aaae6"
+color-link tab-error "#d75f5f"
+color-link trailingws "#d75f5f"

runtime/colorschemes/geany.micro

@@ -25,3 +25,5 @@ color-link diff-deleted "red"
 color-link gutter-error ",red"
 color-link gutter-warning "red"
 color-link match-brace "black,cyan"
+color-link tab-error "brightred"
+color-link trailingws "brightred"

runtime/colorschemes/gotham.micro

@@ -25,3 +25,5 @@ color-link cursor-line "#091F2E"
 color-link color-column "#11151C"
 color-link symbol "#99D1CE,#0C1014"
 color-link match-brace "#0C1014,#D26937"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/gruvbox-tc.micro

@@ -25,3 +25,5 @@ color-link color-column "#79740e"
 color-link statusline "#ebdbb2,#665c54"
 color-link tabbar "#ebdbb2,#665c54"
 color-link match-brace "#282828,#d3869b"
+color-link tab-error "#d75f5f"
+color-link trailingws "#d75f5f"

runtime/colorschemes/gruvbox.micro

@@ -22,3 +22,5 @@ color-link color-column "237"
 color-link statusline "223,237"
 color-link tabbar "223,237"
 color-link match-brace "235,72"
+color-link tab-error "167"
+color-link trailingws "167"

runtime/colorschemes/material-tc.micro

@@ -31,3 +31,5 @@ color-link todo "bold #C792EA,#263238"
 color-link type "#FFCB6B,#263238"
 color-link underlined "underline #EEFFFF,#263238"
 color-link match-brace "#263238,#C792EA"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/monokai-dark.micro

@@ -24,3 +24,5 @@ color-link gutter-warning "#E6DB74"
 color-link cursor-line "#323232"
 color-link color-column "#323232"
 color-link match-brace "#1D0000,#AE81FF"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/monokai.micro

@@ -30,3 +30,5 @@ color-link type.extended "default"
 #color-link symbol.brackets "default"
 color-link symbol.tag "#AE81FF,#282828"
 color-link match-brace "#282828,#AE81FF"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/one-dark.micro

@@ -35,3 +35,5 @@ color-link type "#66D9EF"
 color-link type.keyword "#C678DD"
 color-link underlined "#8996A8"
 color-link match-brace "#21252C,#C678DD"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/railscast.micro

@@ -28,6 +28,8 @@ color-link tabbar "bold #b1b1b1,#232323"
 color-link cursor-line "#353535"
 color-link color-column "#353535"
 color-link space "underline #e6e1dc,#2b2b2b"
+color-link tab-error "#d75f5f"
+color-link trailingws "#d75f5f"
 
 #the Python syntax definition are wrong. This is not how you should do decorators!
 color-link brightgreen "#edb753,#2b2b2b"

runtime/colorschemes/simple.micro

@@ -29,3 +29,5 @@ color-link symbol.brackets "default"
 #Color shebangs the comment color
 color-link preproc.shebang "comment"
 color-link match-brace ",magenta"
+color-link tab-error "brightred"
+color-link trailingws "brightred"

runtime/colorschemes/solarized-tc.micro

@@ -27,3 +27,5 @@ color-link color-column "#003541"
 color-link type.extended "#839496,#002833"
 color-link symbol.brackets "#839496,#002833"
 color-link match-brace "#002833,#268BD2"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/solarized.micro

@@ -26,3 +26,5 @@ color-link color-column "black"
 color-link type.extended "default"
 color-link symbol.brackets "default"
 color-link match-brace ",blue"
+color-link tab-error "brightred"
+color-link trailingws "brightred"

runtime/colorschemes/sunny-day.micro

@@ -25,3 +25,5 @@ color-link cursor-line "229"
 #color-link color-column "196"
 color-link current-line-number "246"
 color-line match-brace "230,22"
+color-link tab-error "210"
+color-link trailingws "210"

runtime/colorschemes/twilight.micro

@@ -36,3 +36,5 @@ color-link type "#F9EE98"
 color-link type.keyword "#CDA869"
 color-link underlined "#8996A8"
 color-link match-brace "#141414,#E0C589"
+color-link tab-error "#D75F5F"
+color-link trailingws "#D75F5F"

runtime/colorschemes/zenburn.micro

@@ -26,3 +26,5 @@ color-link cursor-line "238"
 color-link color-column "238"
 color-link current-line-number "188,237"
 color-link match-brace "237,223"
+color-link tab-error "167"
+color-link trailingws "167"