CLI: Fix TAP compliance for test plan when using QUnit.test.only()

Cherry-picked from 2fcafa4 (3.0.0-dev).

> We correctly prevent registration, counting, and execution of non-only
> tests after the first QUnit.test.only call. And we correctly undo
> the execution and registration of any QUnit.test calls before the
> first QUnit.test.only call.

> But, we did not clear the test *count*. This left the test count
> emitted in `runEnd` event, and thus in the "1..X" test plan printed
> by the TAP reporter, inaccurate. This has implications for TAP-based
> test runners (such as QTap) as those rely on this being accurate to
> declare a run as finished, stop waiting for results, and stop the
> browser process.

Author: Krinkle

src/module.js

@@ -135,6 +135,41 @@ function processModule (name, options, scope, modifiers = {}) {
   }
 }
 
+/**
+ * Clear the SuiteReport tree of all tests and leave only current module as child suite
+ *
+ * This should be called before defining the first module.only() or test.only()
+ * because otherwise:
+ * - `runEnd.testCounts` is too high.
+ * - UI (HtmlReporter) and TAP (TapReporter) display totals too high.
+ * - Test runners like QTap might timeout because the TAP plan
+ *   would be printed as "1..9" even if only 2 tests are run,
+ *   which means tap-finished will wait for 3-9.
+ */
+export function clearSuiteReports (currentModule) {
+  let childSuite = null;
+  let suiteReport = currentModule.suiteReport;
+  while (suiteReport) {
+    suiteReport.tests.length = 0;
+    const i = suiteReport.childSuites.indexOf(childSuite);
+    if (i === -1) {
+      suiteReport.childSuites.length = 0;
+    } else {
+      // Reduce in-place to just currentModule.suiteReport or its intermediary
+      suiteReport.childSuites.splice(0, i);
+      suiteReport.childSuites.splice(1);
+    }
+
+    if (suiteReport === runSuite) {
+      suiteReport = null;
+    } else {
+      childSuite = suiteReport;
+      currentModule = currentModule.parentModule;
+      suiteReport = (currentModule && currentModule.suiteReport) || runSuite;
+    }
+  }
+}
+
 let focused = false; // indicates that the "only" filter was used
 
 export function module (name, options, scope) {
@@ -149,6 +184,7 @@ module.only = function (...args) {
     // delete any and all previously registered modules and tests.
     config.modules.length = 0;
     config.queue.length = 0;
+    clearSuiteReports(config.currentModule);
 
     // Ignore any tests declared after this block within the same
     // module parent. https://github.com/qunitjs/qunit/issues/1645

src/test.js

@@ -2,6 +2,7 @@ import { globalThis, setTimeout, clearTimeout, StringMap } from './globals';
 import { emit } from './events';
 import Assert from './assert';
 import Logger from './logger';
+import { clearSuiteReports } from './module';
 import Promise from './promise';
 
 import config from './core/config';
@@ -979,6 +980,8 @@ function addOnlyTest (settings) {
   }
   if (!focused) {
     config.queue.length = 0;
+    clearSuiteReports(config.currentModule);
+
     focused = true;
   }
 

test/cli/fixtures/only-module-flat.tap.txt

@@ -12,8 +12,8 @@ not ok 1 module B > test B # TODO
   ...
 ok 2 module B > test C # SKIP
 ok 3 module B > test D
-1..4
-# pass 2
+1..3
+# pass 1
 # skip 1
 # todo 1
 # fail 0

test/cli/fixtures/only-module-then-test.tap.txt

@@ -3,8 +3,8 @@
 
 TAP version 13
 ok 1 module A > module B > test B
-1..2
-# pass 2
+1..1
+# pass 1
 # skip 0
 # todo 0
 # fail 0

test/cli/fixtures/only-module.tap.txt

@@ -16,8 +16,8 @@ ok 3 module B > Only this module should run > normal test
 ok 4 module D > test D
 ok 5 module E > module F > test F
 ok 6 module E > test E
-1..8
-# pass 6
+1..6
+# pass 4
 # skip 1
 # todo 1
 # fail 0

test/cli/fixtures/only-test.tap.txt

@@ -4,8 +4,8 @@
 TAP version 13
 ok 1 run this test
 ok 2 all tests with only run
-1..3
-# pass 3
+1..2
+# pass 2
 # skip 0
 # todo 0
 # fail 0