From c0251d31d27142b569bd4a16ced6073bbcda6150 Mon Sep 17 00:00:00 2001
From: Nikhil Benesch <nikhil.benesch@gmail.com>
Date: Mon, 12 Feb 2018 19:48:13 -0500
Subject: [PATCH] imports: handle arbitrarily long lines

Previous work to resolve golang/go#18201 increased the maximum line
length that goimports could handle to 1MiB (CL83800), but generated code
can result in Go files with longer lines. Use a bufio.Reader instead of
a bufio.Scanner to support arbitrarily long lines, as permitted by the
Go spec.

Change-Id: If719e531859804304d60a8c00db6304ab3d5fe5e
Reviewed-on: https://go-review.googlesource.com/93439
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
---
 imports/fix_test.go | 27 ---------------------------
 imports/imports.go  | 20 ++++++++++----------
 2 files changed, 10 insertions(+), 37 deletions(-)

diff --git a/imports/fix_test.go b/imports/fix_test.go
index 30985528..bb5fcb9e 100644
--- a/imports/fix_test.go
+++ b/imports/fix_test.go
@@ -5,7 +5,6 @@
 package imports
 
 import (
-	"bufio"
 	"bytes"
 	"flag"
 	"go/build"
@@ -2033,29 +2032,3 @@ const x = mypkg.Sprintf("%s", "my package")
 		t.Errorf("Process returned unexpected result.\ngot:\n%v\nwant:\n%v", got, want)
 	}
 }
-
-// Ensures a token that is larger that
-// https://golang.org/issues/18201
-func TestProcessTokenTooLarge(t *testing.T) {
-	const largeSize = maxScanTokenSize + 1
-	largeString := strings.Repeat("x", largeSize)
-
-	in := `package testimports
-
-import (
-	"fmt"
-	"mydomain.mystuff/mypkg"
-)
-
-const s = fmt.Sprintf("%s", "` + largeString + `")
-const x = mypkg.Sprintf("%s", "my package")
-
-// end
-`
-
-	_, err := Process("foo", []byte(in), nil)
-
-	if err != bufio.ErrTooLong {
-		t.Errorf("Process did not returned expected error.\n got:\n%v\nwant:\n%v", err, bufio.ErrTooLong)
-	}
-}
diff --git a/imports/imports.go b/imports/imports.go
index d789bb5b..bd67f91d 100644
--- a/imports/imports.go
+++ b/imports/imports.go
@@ -259,18 +259,18 @@ func matchSpace(orig []byte, src []byte) []byte {
 
 var impLine = regexp.MustCompile(`^\s+(?:[\w\.]+\s+)?"(.+)"`)
 
-// Used to set Scanner buffer size so that large tokens can be handled.
-// see https://github.com/golang/go/issues/18201
-const maxScanTokenSize = bufio.MaxScanTokenSize * 16
-
 func addImportSpaces(r io.Reader, breaks []string) ([]byte, error) {
 	var out bytes.Buffer
-	sc := bufio.NewScanner(r)
-	sc.Buffer(nil, maxScanTokenSize)
+	in := bufio.NewReader(r)
 	inImports := false
 	done := false
-	for sc.Scan() {
-		s := sc.Text()
+	for {
+		s, err := in.ReadString('\n')
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
 
 		if !inImports && !done && strings.HasPrefix(s, "import") {
 			inImports = true
@@ -291,7 +291,7 @@ func addImportSpaces(r io.Reader, breaks []string) ([]byte, error) {
 			}
 		}
 
-		fmt.Fprintln(&out, s)
+		fmt.Fprint(&out, s)
 	}
-	return out.Bytes(), sc.Err()
+	return out.Bytes(), nil
 }