Only recognize well-known comment markers

Restricting what comment markers keep-sorted accepts leads to less
surprising behavior, such as // go/keep-sorted treating the comment
marker as "// go/" when using the default id of just "keep-sorted".

README.md

@@ -179,8 +179,10 @@ allows for sorting data such as Go structs and JSON objects.
 #### Comments
 
 Comments embedded within the sorted block are made to stick with their
-successor. The comment lines must start with the same token as the
-keep-sorted instruction itself (e.g. `#` in the case below).
+successor. The comment lines must start with the same comment marker as the
+keep-sorted instruction itself (e.g. `#` in the case below). keep-sorted
+will recognize `//`, `/*`, `#`, `--`, `;`, and `<!--` as comment markers, for
+any other kinds of comments, use `sticky_prefixes`.
 
 This special handling can be disabled by specifying the parameter
 `sticky_comments=no`:

keepsorted/keep_sorted_test.go

@@ -168,6 +168,95 @@ baz
 foo
 // keep-sorted-test end`,
  },
+ {
+ name: "sticky comment with prefix to id",
+
+ in: `
+// some prefix (normally this is go/) keep-sorted-test start
+2
+1
+// comment on 3
+3
+// keep-sorted-test end
+
+# some prefix (normally this is go/) keep-sorted-test start
+2
+1
+# comment on 3
+3
+# keep-sorted-test end
+
+/* some prefix (normally this is go/) keep-sorted-test start */
+2
+1
+/* comment on 3 */
+3
+/* keep-sorted-test end */
+
+-- some prefix (normally this is go/) keep-sorted-test start
+2
+1
+-- comment on 3
+3
+-- keep-sorted-test end
+
+; some prefix (normally this is go/) keep-sorted-test start
+2
+1
+; comment on 3
+3
+; keep-sorted-test end
+
+<!-- some prefix (normally this is go/) keep-sorted-test start -->
+2
+1
+<!-- comment on 3 -->
+3
+<!-- keep-sorted-test end -->`,
+
+ want: `
+// some prefix (normally this is go/) keep-sorted-test start
+1
+2
+// comment on 3
+3
+// keep-sorted-test end
+
+# some prefix (normally this is go/) keep-sorted-test start
+1
+2
+# comment on 3
+3
+# keep-sorted-test end
+
+/* some prefix (normally this is go/) keep-sorted-test start */
+1
+2
+/* comment on 3 */
+3
+/* keep-sorted-test end */
+
+-- some prefix (normally this is go/) keep-sorted-test start
+1
+2
+-- comment on 3
+3
+-- keep-sorted-test end
+
+; some prefix (normally this is go/) keep-sorted-test start
+1
+2
+; comment on 3
+3
+; keep-sorted-test end
+
+<!-- some prefix (normally this is go/) keep-sorted-test start -->
+1
+2
+<!-- comment on 3 -->
+3
+<!-- keep-sorted-test end -->`,
+ },
  } {
  t.Run(tc.name, func(t *testing.T) {
  got, gotAlreadyFixed := New("keep-sorted-test").Fix(tc.in, nil)

keepsorted/options.go

@@ -180,8 +180,21 @@ func parseValueWithDefault(f reflect.StructField, key, val string, defaultFn fun
 }
 
 func (f *Fixer) guessCommentMarker(startLine string) string {
- sp := strings.SplitN(startLine, f.ID, 2)
- return strings.TrimSpace(sp[0])
+ startLine = strings.TrimSpace(startLine)
+ if strings.HasPrefix(startLine, "//") {
+ return "//"
+ } else if strings.HasPrefix(startLine, "#") {
+ return "#"
+ } else if strings.HasPrefix(startLine, "/*") {
+ return "/*"
+ } else if strings.HasPrefix(startLine, "--") {
+ return "--"
+ } else if strings.HasPrefix(startLine, ";") {
+ return ";"
+ } else if strings.HasPrefix(startLine, "<!--") {
+ return "<!--"
+ }
+ return ""
 }
 
 // hasStickyPrefix determines if s has one of the StickyPrefixes.