feat: add Subtest to tap protocol output

PR-URL: nodejs/node#43417
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/test_runner/tap_stream.js

@@ -1,4 +1,4 @@
-// https://github.com/nodejs/node/blob/1aab13cad9c800f4121c1d35b554b78c1b17bdbd/lib/internal/test_runner/tap_stream.js
+// https://github.com/nodejs/node/blob/5fadc389b8a9a32809adda8245ad32928623409b/lib/internal/test_runner/tap_stream.js
 
 'use strict'
 
@@ -75,6 +75,10 @@ class TapStream extends Readable {
     return `TODO${reason ? ` ${tapEscape(reason)}` : ''}`
   }
 
+  subtest (indent, name) {
+    this.#tryPush(`${indent}# Subtest: ${tapEscape(name)}\n`)
+  }
+
   details (indent, duration, error) {
     let details = `${indent}  ---\n`
 

lib/internal/test_runner/test.js

@@ -1,4 +1,4 @@
-// https://github.com/nodejs/node/blob/44aa46d70537d3807bd9255db77f76cd9dea5267/lib/internal/test_runner/test.js
+// https://github.com/nodejs/node/blob/5fadc389b8a9a32809adda8245ad32928623409b/lib/internal/test_runner/test.js
 
 'use strict'
 
@@ -188,6 +188,10 @@ class Test extends AsyncResource {
         return
       }
 
+      if (i === 1 && this.parent !== null) {
+        this.reporter.subtest(this.indent, this.name)
+      }
+
       // Report the subtest's results and remove it from the ready map.
       subtest.finalize()
       this.readySubtests.delete(i)
@@ -421,6 +425,8 @@ class Test extends AsyncResource {
     // Output this test's results and update the parent's waiting counter.
     if (this.subtests.length > 0) {
       this.reporter.plan(this.subtests[0].indent, this.subtests.length)
+    } else {
+      this.reporter.subtest(this.indent, this.name)
     }
 
     this.report()

test/message/test_runner_no_refs.out

@@ -1,4 +1,6 @@
 TAP version 13
+# Subtest: does not keep event loop alive
+    # Subtest: +does not keep event loop alive
     not ok 1 - +does not keep event loop alive
       ---
       duration_ms: *

test/message/test_runner_only_tests.out

@@ -1,76 +1,97 @@
 TAP version 13
+# Subtest: only = undefined
 ok 1 - only = undefined # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = undefined, skip = string
 ok 2 - only = undefined, skip = string # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = undefined, skip = true
 ok 3 - only = undefined, skip = true # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = undefined, skip = false
 ok 4 - only = undefined, skip = false # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = false
 ok 5 - only = false # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = false, skip = string
 ok 6 - only = false, skip = string # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = false, skip = true
 ok 7 - only = false, skip = true # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = false, skip = false
 ok 8 - only = false, skip = false # SKIP 'only' option not set
   ---
   duration_ms: *
   ...
+# Subtest: only = true, skip = string
 ok 9 - only = true, skip = string # SKIP skip message
   ---
   duration_ms: *
   ...
+# Subtest: only = true, skip = true
 ok 10 - only = true, skip = true # SKIP
   ---
   duration_ms: *
   ...
+# Subtest: only = true, with subtests
+    # Subtest: running subtest 1
     ok 1 - running subtest 1
       ---
       duration_ms: *
       ...
+    # Subtest: running subtest 2
     ok 2 - running subtest 2
       ---
       duration_ms: *
       ...
+    # Subtest: skipped subtest 1
     ok 3 - skipped subtest 1 # SKIP 'only' option not set
       ---
       duration_ms: *
       ...
+    # Subtest: skipped subtest 2
     ok 4 - skipped subtest 2 # SKIP 'only' option not set
       ---
       duration_ms: *
       ...
+    # Subtest: running subtest 3
     ok 5 - running subtest 3
       ---
       duration_ms: *
       ...
+    # Subtest: running subtest 4
+        # Subtest: running sub-subtest 1
         ok 1 - running sub-subtest 1
           ---
           duration_ms: *
           ...
+        # Subtest: running sub-subtest 2
         ok 2 - running sub-subtest 2
           ---
           duration_ms: *
           ...
+        # Subtest: skipped sub-subtest 1
         ok 3 - skipped sub-subtest 1 # SKIP 'only' option not set
           ---
           duration_ms: *
           ...
+        # Subtest: skipped sub-subtest 2
         ok 4 - skipped sub-subtest 2 # SKIP 'only' option not set
           ---
           duration_ms: *
@@ -80,10 +101,12 @@ ok 10 - only = true, skip = true # SKIP
       ---
       duration_ms: *
       ...
+    # Subtest: skipped subtest 3
     ok 7 - skipped subtest 3 # SKIP 'only' option not set
       ---
       duration_ms: *
       ...
+    # Subtest: skipped subtest 4
     ok 8 - skipped subtest 4 # SKIP
       ---
       duration_ms: *