issue: fix nil pointer dereference on plumb error

plumbserve() fails with a nil pointer dereference when it tries to
print errors via w.Err(). This happens because w is a dummy window
with a nil *acme.Win. This commit  replaces w.Err() calls in
plumbserve() with acme.Errf(). It also extracts the plumbserve()
method out of *awin, given that the previous change removes this
dependency.

Fixes issue rsc#5.

issue/acme.go

@@ -14,6 +14,7 @@ import (
  "fmt"
  "log"
  "os"
+ "path"
  "regexp"
  "strconv"
  "strings"
@@ -25,9 +26,11 @@ import (
  "github.com/google/go-github/github"
 )
 
+const root = "/issue/"
+
 func (w *awin) project() string {
  p := w.prefix
- p = strings.TrimPrefix(p, "/issue/")
+ p = strings.TrimPrefix(p, root)
  i := strings.Index(p, "/")
  if i >= 0 {
  j := strings.Index(p[i+1:], "/")
@@ -40,7 +43,7 @@ func (w *awin) project() string {
 
 func acmeMode() {
  var dummy awin
- dummy.prefix = "/issue/" + *project + "/"
+ dummy.prefix = path.Join(root, *project) + "/"
  if flag.NArg() > 0 {
  // TODO(rsc): Without -a flag, the query is conatenated into one query.
  // Decide which behavior should be used, and use it consistently.
@@ -59,59 +62,59 @@ func acmeMode() {
  dummy.Look("all")
  }
 
- go dummy.plumbserve()
+ go plumbserve()
 
  select {}
 }
 
-func (w *awin) plumbserve() {
+func plumbserve() {
  fid, err := plumb.Open("githubissue", 0)
  if err != nil {
- w.Err(fmt.Sprintf("plumb: %v", err))
+ acme.Errf(root, "plumb: %v", err)
  return
  }
  r := bufio.NewReader(fid)
  for {
  var m plumb.Message
  if err := m.Recv(r); err != nil {
- w.Err(fmt.Sprintf("plumb recv: %v", err))
+ acme.Errf(root, "plumb recv: %v", err)
  return
  }
  if m.Type != "text" {
- w.Err(fmt.Sprintf("plumb recv: unexpected type: %s\n", m.Type))
+ acme.Errf(root, "plumb recv: unexpected type: %s", m.Type)
  continue
  }
  if m.Dst != "githubissue" {
- w.Err(fmt.Sprintf("plumb recv: unexpected dst: %s\n", m.Dst))
+ acme.Errf(root, "plumb recv: unexpected dst: %s", m.Dst)
  continue
  }
  // TODO use m.Dir
  data := string(m.Data)
  var project, what string
- if strings.HasPrefix(data, "/issue/") {
- project = data[len("/issue/"):]
+ if strings.HasPrefix(data, root) {
+ project = data[len(root):]
  i := strings.LastIndex(project, "/")
  if i < 0 {
- w.Err(fmt.Sprintf("plumb recv: bad text %q", data))
+ acme.Errf(root, "plumb recv: bad text %q", data)
  continue
  }
  project, what = project[:i], project[i+1:]
  } else {
  i := strings.Index(data, "#")
  if i < 0 {
- w.Err(fmt.Sprintf("plumb recv: bad text %q", data))
+ acme.Errf(root, "plumb recv: bad text %q", data)
  continue
  }
  project, what = data[:i], data[i+1:]
  }
  if strings.Count(project, "/") != 1 {
- w.Err(fmt.Sprintf("plumb recv: bad text %q", data))
+ acme.Errf(root, "plumb recv: bad text %q", data)
  continue
  }
  var plummy awin
- plummy.prefix = "/issue/" + project + "/"
+ plummy.prefix = path.Join(root, project) + "/"
  if !plummy.Look(what) {
- w.Err(fmt.Sprintf("plumb recv: can't look %s%s", plummy.prefix, what))
+ acme.Errf(root, "plumb recv: can't look %s%s", plummy.prefix, what)
  }
  }
 }
@@ -251,7 +254,7 @@ func (w *awin) Look(text string) bool {
  if m := repoHashRE.FindStringSubmatch(text); m != nil {
  project := m[1]
  what := m[2]
- prefix := "/issue/" + project + "/"
+ prefix := path.Join(root, project) + "/"
  if acme.Show(prefix+what) != nil {
  return true
  }