move the unrelated "Joiner" out of "js_printer"

internal/bundler/linker.go

@@ -17,6 +17,7 @@ import (
 	"github.com/evanw/esbuild/internal/css_ast"
 	"github.com/evanw/esbuild/internal/css_printer"
 	"github.com/evanw/esbuild/internal/fs"
+	"github.com/evanw/esbuild/internal/helpers"
 	"github.com/evanw/esbuild/internal/js_ast"
 	"github.com/evanw/esbuild/internal/js_lexer"
 	"github.com/evanw/esbuild/internal/js_printer"
@@ -3789,7 +3790,7 @@ func (repr *chunkReprJS) generate(c *linkerContext, chunk *chunkInfo) func(gener
 
 		waitGroup.Wait()
 
-		j := js_printer.Joiner{}
+		j := helpers.Joiner{}
 		prevOffset := sourcemap.LineColumnOffset{}
 
 		// Optionally strip whitespace
@@ -4263,7 +4264,7 @@ func (repr *chunkReprCSS) generate(c *linkerContext, chunk *chunkInfo) func(gene
 	// Wait for cross-chunk import records before continuing
 	return func(continueData generateContinue) []OutputFile {
 		waitGroup.Wait()
-		j := js_printer.Joiner{}
+		j := helpers.Joiner{}
 		newlineBeforeComment := false
 
 		if len(c.options.CSSBanner) > 0 {
@@ -4513,7 +4514,7 @@ func (c *linkerContext) generateSourceMapForChunk(
 	chunkAbsDir string,
 	dataForSourceMaps []dataForSourceMap,
 ) []byte {
-	j := js_printer.Joiner{}
+	j := helpers.Joiner{}
 	j.AddString("{\n  \"version\": 3")
 
 	// Only write out the sources for a given source index once

internal/helpers/joiner.go

@@ -0,0 +1,57 @@
+package helpers
+
+// This provides an efficient way to join lots of big string and byte slices
+// together. It avoids the cost of repeatedly reallocating as the buffer grows
+// by measuring exactly how big the buffer should be and then allocating once.
+// This is a measurable speedup.
+type Joiner struct {
+	lastByte byte
+	strings  []joinerString
+	bytes    []joinerBytes
+	length   uint32
+}
+
+type joinerString struct {
+	data   string
+	offset uint32
+}
+
+type joinerBytes struct {
+	data   []byte
+	offset uint32
+}
+
+func (j *Joiner) AddString(data string) {
+	if len(data) > 0 {
+		j.lastByte = data[len(data)-1]
+	}
+	j.strings = append(j.strings, joinerString{data, j.length})
+	j.length += uint32(len(data))
+}
+
+func (j *Joiner) AddBytes(data []byte) {
+	if len(data) > 0 {
+		j.lastByte = data[len(data)-1]
+	}
+	j.bytes = append(j.bytes, joinerBytes{data, j.length})
+	j.length += uint32(len(data))
+}
+
+func (j *Joiner) LastByte() byte {
+	return j.lastByte
+}
+
+func (j *Joiner) Length() uint32 {
+	return j.length
+}
+
+func (j *Joiner) Done() []byte {
+	buffer := make([]byte, j.length)
+	for _, item := range j.strings {
+		copy(buffer[item.offset:], item.data)
+	}
+	for _, item := range j.bytes {
+		copy(buffer[item.offset:], item.data)
+	}
+	return buffer
+}

internal/js_printer/js_printer.go

@@ -11,6 +11,7 @@ import (
 	"github.com/evanw/esbuild/internal/ast"
 	"github.com/evanw/esbuild/internal/compat"
 	"github.com/evanw/esbuild/internal/config"
+	"github.com/evanw/esbuild/internal/helpers"
 	"github.com/evanw/esbuild/internal/js_ast"
 	"github.com/evanw/esbuild/internal/js_lexer"
 	"github.com/evanw/esbuild/internal/logger"
@@ -45,7 +46,7 @@ type SourceMapState struct {
 // After all chunks are computed, they are joined together in a second pass.
 // This rewrites the first mapping in each chunk to be relative to the end
 // state of the previous chunk.
-func AppendSourceMapChunk(j *Joiner, prevEndState SourceMapState, startState SourceMapState, sourceMap []byte) {
+func AppendSourceMapChunk(j *helpers.Joiner, prevEndState SourceMapState, startState SourceMapState, sourceMap []byte) {
 	// Handle line breaks in between this mapping and the previous one
 	if startState.GeneratedLine != 0 {
 		j.AddBytes(bytes.Repeat([]byte{';'}, startState.GeneratedLine))
@@ -80,7 +81,7 @@ func AppendSourceMapChunk(j *Joiner, prevEndState SourceMapState, startState Sou
 	startState.GeneratedColumn += generatedColumn
 	startState.OriginalLine += originalLine
 	startState.OriginalColumn += originalColumn
-	j.AddBytes(appendMapping(nil, j.lastByte, prevEndState, startState))
+	j.AddBytes(appendMapping(nil, j.LastByte(), prevEndState, startState))
 
 	// Then append everything after that without modification.
 	j.AddBytes(sourceMap)
@@ -111,62 +112,6 @@ func appendMapping(buffer []byte, lastByte byte, prevState SourceMapState, curre
 	return buffer
 }
 
-// This provides an efficient way to join lots of big string and byte slices
-// together. It avoids the cost of repeatedly reallocating as the buffer grows
-// by measuring exactly how big the buffer should be and then allocating once.
-// This is a measurable speedup.
-type Joiner struct {
-	lastByte byte
-	strings  []joinerString
-	bytes    []joinerBytes
-	length   uint32
-}
-
-type joinerString struct {
-	data   string
-	offset uint32
-}
-
-type joinerBytes struct {
-	data   []byte
-	offset uint32
-}
-
-func (j *Joiner) AddString(data string) {
-	if len(data) > 0 {
-		j.lastByte = data[len(data)-1]
-	}
-	j.strings = append(j.strings, joinerString{data, j.length})
-	j.length += uint32(len(data))
-}
-
-func (j *Joiner) AddBytes(data []byte) {
-	if len(data) > 0 {
-		j.lastByte = data[len(data)-1]
-	}
-	j.bytes = append(j.bytes, joinerBytes{data, j.length})
-	j.length += uint32(len(data))
-}
-
-func (j *Joiner) LastByte() byte {
-	return j.lastByte
-}
-
-func (j *Joiner) Length() uint32 {
-	return j.length
-}
-
-func (j *Joiner) Done() []byte {
-	buffer := make([]byte, j.length)
-	for _, item := range j.strings {
-		copy(buffer[item.offset:], item.data)
-	}
-	for _, item := range j.bytes {
-		copy(buffer[item.offset:], item.data)
-	}
-	return buffer
-}
-
 const hexChars = "0123456789ABCDEF"
 const firstASCII = 0x20
 const lastASCII = 0x7E