enable hashes in entry file paths (#1001)

internal/sourcemap/sourcemap.go

@@ -3,6 +3,8 @@ package sourcemap
 import (
 	"bytes"
 	"unicode/utf8"
+
+	"github.com/evanw/esbuild/internal/helpers"
 )
 
 type Mapping struct {
@@ -184,6 +186,19 @@ type LineColumnOffset struct {
 	Columns int
 }
 
+func (a LineColumnOffset) ComesBefore(b LineColumnOffset) bool {
+	return a.Lines < b.Lines || (a.Lines == b.Lines && a.Columns < b.Columns)
+}
+
+func (a *LineColumnOffset) Add(b LineColumnOffset) {
+	if b.Lines == 0 {
+		a.Columns += b.Columns
+	} else {
+		a.Lines += b.Lines
+		a.Columns = b.Columns
+	}
+}
+
 func (offset *LineColumnOffset) AdvanceBytes(bytes []byte) {
 	columns := offset.Columns
 	for len(bytes) > 0 {
@@ -237,3 +252,109 @@ func (offset *LineColumnOffset) AdvanceString(text string) {
 	}
 	offset.Columns = columns
 }
+
+type SourceMapPieces struct {
+	Prefix   []byte
+	Mappings []byte
+	Suffix   []byte
+}
+
+type SourceMapShift struct {
+	Before LineColumnOffset
+	After  LineColumnOffset
+}
+
+func (pieces SourceMapPieces) Finalize(shifts []SourceMapShift) []byte {
+	// An optimized path for when there are no shifts
+	if len(shifts) == 1 {
+		bytes := pieces.Prefix
+		minCap := len(bytes) + len(pieces.Mappings) + len(pieces.Suffix)
+		if cap(bytes) < minCap {
+			bytes = append(make([]byte, 0, minCap), bytes...)
+		}
+		bytes = append(bytes, pieces.Mappings...)
+		bytes = append(bytes, pieces.Suffix...)
+		return bytes
+	}
+
+	startOfRun := 0
+	current := 0
+	generated := LineColumnOffset{}
+	prevShiftColumnDelta := 0
+	j := helpers.Joiner{}
+
+	// Start the source map
+	j.AddBytes(pieces.Prefix)
+
+	// This assumes that a) all mappings are valid and b) all mappings are ordered
+	// by increasing generated position. This should be the case for all mappings
+	// generated by esbuild, which should be the only mappings we process here.
+	for current < len(pieces.Mappings) {
+		// Handle a line break
+		if pieces.Mappings[current] == ';' {
+			generated.Lines++
+			generated.Columns = 0
+			prevShiftColumnDelta = 0
+			current++
+			continue
+		}
+
+		potentialEndOfRun := current
+
+		// Read the generated column
+		generatedColumnDelta, next := DecodeVLQ(pieces.Mappings, current)
+		generated.Columns += generatedColumnDelta
+		current = next
+
+		potentialStartOfRun := current
+
+		// Skip over the original position information
+		_, current = DecodeVLQ(pieces.Mappings, current) // The original source
+		_, current = DecodeVLQ(pieces.Mappings, current) // The original line
+		_, current = DecodeVLQ(pieces.Mappings, current) // The original column
+
+		// Skip a trailing comma
+		if current < len(pieces.Mappings) && pieces.Mappings[current] == ',' {
+			current++
+		}
+
+		// Detect crossing shift boundaries
+		didCrossBoundary := false
+		for len(shifts) > 1 && shifts[1].Before.ComesBefore(generated) {
+			shifts = shifts[1:]
+			didCrossBoundary = true
+		}
+		if !didCrossBoundary {
+			continue
+		}
+
+		// This shift isn't relevant if the next mapping after this shift is on a
+		// following line. In that case, don't split and keep scanning instead.
+		shift := shifts[0]
+		if shift.After.Lines != generated.Lines {
+			continue
+		}
+
+		// Add all previous mappings in a single run for efficiency. Since source
+		// mappings are relative, no data needs to be modified inside this run.
+		j.AddBytes(pieces.Mappings[startOfRun:potentialEndOfRun])
+
+		// Then modify the first mapping across the shift boundary with the updated
+		// generated column value. It's simplest to only support column shifts. This
+		// is reasonable because import paths should not contain newlines.
+		if shift.Before.Lines != shift.After.Lines {
+			panic("Unexpected line change when shifting source maps")
+		}
+		shiftColumnDelta := shift.After.Columns - shift.Before.Columns
+		j.AddBytes(EncodeVLQ(generatedColumnDelta + shiftColumnDelta - prevShiftColumnDelta))
+		prevShiftColumnDelta = shiftColumnDelta
+
+		// Finally, start the next run after the end of this generated column offset
+		startOfRun = potentialStartOfRun
+	}
+
+	// Finish the source map
+	j.AddBytes(pieces.Mappings[startOfRun:])
+	j.AddBytes(pieces.Suffix)
+	return j.Done()
+}