x/tools/cmd/goimports: moves comment to inappropriate line

[dfawley]

Create a file with the following contents:

package main

import (
	"math" // fun
)

func main() {
	x := math.MaxInt64
	fmt.Println(strings.Join(",", []string{"hi"}), x)
}

$ goimports -d /tmp/a.go
diff -u /tmp/a.go.orig /tmp/a.go
--- /tmp/a.go.orig	2018-02-05 15:44:54.612402902 -0800
+++ /tmp/a.go	2018-02-05 15:44:54.612402902 -0800
@@ -1,7 +1,9 @@
 package main
 
 import (
-	"math" // fun
+	"fmt"
+	"math"
+	"strings" // fun
 )
 
 func main() {

Expected:

$ goimports -d /tmp/a.go
diff -u /tmp/a.go.orig /tmp/a.go
--- /tmp/a.go.orig	2018-02-05 15:44:54.612402902 -0800
+++ /tmp/a.go	2018-02-05 15:44:54.612402902 -0800
@@ -1,7 +1,9 @@
 package main
 
 import (
+	"fmt"
	"math" // fun
+	"strings"
 )
 
 func main() {

Versions tested:

go version go1.10rc1 linux/amd64
go version go1.9.3 linux/amd64

[gopherbot]

Change https://golang.org/cl/93055 mentions this issue: imports: fixup comments on import lines correctly

[cuonglm]

@bradfitz Can you take a look?

[lukelafountaine]

I would like to start contributing to Go. Would this be a good issue to cut my teeth on?

[ianlancetaylor]

@lukelafountaine it looks like someone may have already sent a patch for this--see the comment about CL 93055 above.

[cuonglm]

I'm not sure it's a problem, but this line:

https://github.com/golang/tools/blob/master/go/ast/astutil/imports.go#L141

set all imported line to the same position in file, then when sorting it, the current position is tracked:

https://github.com/golang/tools/blob/master/imports/sortimports.go#L106

In this example, math and strings both have EndPos at 38, the same for // fun, so it ends up display beside strings.

[gopherbot]

Change https://golang.org/cl/121878 mentions this issue: imports: fixup comments on import lines correctly

[cuonglm]

cc @bradfitz I sent new CL for this issue, please take a look

[ncw]

This change appears to have broken goimports in a different way putting spurious blank lines after import lines with comments.

~/go/src/github.com/ncw/rclone$ find . -name *.go | grep -v /vendor/ | xargs goimports -d

diff -u ./cmd/serve/webdav/webdav.go.orig ./cmd/serve/webdav/webdav.go
--- ./cmd/serve/webdav/webdav.go.orig	2018-07-03 22:24:12.339811431 +0100
+++ ./cmd/serve/webdav/webdav.go	2018-07-03 22:24:12.339811431 +0100
@@ -16,6 +16,7 @@
 	"github.com/ncw/rclone/vfs/vfsflags"
 	"github.com/spf13/cobra"
 	"golang.org/x/net/context" // switch to "context" when we stop supporting go1.8
+
 	"golang.org/x/net/webdav"
 )
 
diff -u ./fs/rc/rc.go.orig ./fs/rc/rc.go
--- ./fs/rc/rc.go.orig	2018-07-03 22:24:13.099814169 +0100
+++ ./fs/rc/rc.go	2018-07-03 22:24:13.099814169 +0100
@@ -12,6 +12,7 @@
 	"io"
 	"net/http"
 	_ "net/http/pprof" // install the pprof http handlers
+
 	"strings"
 
 	"github.com/ncw/rclone/cmd/serve/httplib"

I don't know if that was intended but before this change goimports didn't insert that spurious blank line.

[bradfitz]

@ncw, could you file a new bug and cc the author on it and reference this bug?