cmd/internal/test2json: support subtests containing colons

The "updates" lines, such as RUN, do not contain a colon. However,
test2json looked for one anyway, meaning that it would be thrown off if
it encountered a line like:

	=== RUN   TestWithColons/[::1]

In that case, it must not use the first colon it encounters to separate
the action from the test name.

Fixes #23920.

Change-Id: I82eff23e24b83dae183c0cf9f85fc5f409f51c25
Reviewed-on: https://go-review.googlesource.com/98445
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/test2json/test2json.go

@@ -175,6 +175,7 @@ func (c *converter) handleInputLine(line []byte) {
 	// "=== RUN   "
 	// "=== PAUSE "
 	// "=== CONT  "
+	actionColon := false
 	origLine := line
 	ok := false
 	indent := 0
@@ -196,6 +197,7 @@ func (c *converter) handleInputLine(line []byte) {
 		}
 		for _, magic := range reports {
 			if bytes.HasPrefix(line, magic) {
+				actionColon = true
 				ok = true
 				break
 			}
@@ -209,7 +211,10 @@ func (c *converter) handleInputLine(line []byte) {
 	}
 
 	// Parse out action and test name.
-	i := bytes.IndexByte(line, ':') + 1
+	i := 0
+	if actionColon {
+		i = bytes.IndexByte(line, ':') + 1
+	}
 	if i == 0 {
 		i = len(updates[0])
 	}

src/cmd/internal/test2json/testdata/issue23920.json

+{"Action":"run","Test":"TestWithColons"}
+{"Action":"output","Test":"TestWithColons","Output":"=== RUN   TestWithColons\n"}
+{"Action":"run","Test":"TestWithColons/[::1]"}
+{"Action":"output","Test":"TestWithColons/[::1]","Output":"=== RUN   TestWithColons/[::1]\n"}
+{"Action":"run","Test":"TestWithColons/127.0.0.1:0"}
+{"Action":"output","Test":"TestWithColons/127.0.0.1:0","Output":"=== RUN   TestWithColons/127.0.0.1:0\n"}
+{"Action":"output","Test":"TestWithColons","Output":"--- PASS: TestWithColons (0.00s)\n"}
+{"Action":"output","Test":"TestWithColons/[::1]","Output":"    --- PASS: TestWithColons/[::1] (0.00s)\n"}
+{"Action":"pass","Test":"TestWithColons/[::1]"}
+{"Action":"output","Test":"TestWithColons/127.0.0.1:0","Output":"    --- PASS: TestWithColons/127.0.0.1:0 (0.00s)\n"}
+{"Action":"pass","Test":"TestWithColons/127.0.0.1:0"}
+{"Action":"pass","Test":"TestWithColons"}
+{"Action":"output","Output":"PASS\n"}
+{"Action":"pass"}

src/cmd/internal/test2json/testdata/issue23920.test

+=== RUN   TestWithColons
+=== RUN   TestWithColons/[::1]
+=== RUN   TestWithColons/127.0.0.1:0
+--- PASS: TestWithColons (0.00s)
+    --- PASS: TestWithColons/[::1] (0.00s)
+    --- PASS: TestWithColons/127.0.0.1:0 (0.00s)
+PASS