run-tests: add a way to list tests, with JSON and XUnit support

Some test runners are interested in listing tests, so they can do their own
filtering on top (usually based on attributes like historically observed
runtime). Add support for that.

tests/run-tests.py

@@ -263,6 +263,8 b' def getparser():'
         help="keep temporary directory after running tests")
     parser.add_option("-k", "--keywords",
         help="run tests matching keywords")
+    parser.add_option("--list-tests", action="store_true",
+        help="list tests instead of running them")
     parser.add_option("-l", "--local", action="store_true",
         help="shortcut for --with-hg=<testdir>/../hg, "
              "and --with-chg=<testdir>/../contrib/chg/chg if --chg is set")
@@ -1907,6 +1909,25 b' class TextTestRunner(unittest.TextTestRu'
 
         self._runner = runner
 
+    def listtests(self, test):
+        result = TestResult(self._runner.options, self.stream,
+                            self.descriptions, 0)
+        test = sorted(test, key=lambda t: t.name)
+        for t in test:
+            print(t.name)
+            result.addSuccess(t)
+
+        if self._runner.options.xunit:
+            with open(self._runner.options.xunit, "wb") as xuf:
+                self._writexunit(result, xuf)
+
+        if self._runner.options.json:
+            jsonpath = os.path.join(self._runner._testdir, b'report.json')
+            with open(jsonpath, 'w') as fp:
+                self._writejson(result, fp)
+
+        return result
+
     def run(self, test):
         result = TestResult(self._runner.options, self.stream,
                             self.descriptions, self.verbosity)
@@ -2384,16 +2405,19 b' class TestRunner(object):'
                 verbosity = 2
             runner = TextTestRunner(self, verbosity=verbosity)
 
-            if self._installdir:
-                self._installhg()
-                self._checkhglib("Testing")
+            if self.options.list_tests:
+                result = runner.listtests(suite)
             else:
-                self._usecorrectpython()
-            if self.options.chg:
-                assert self._installdir
-                self._installchg()
+                if self._installdir:
+                    self._installhg()
+                    self._checkhglib("Testing")
+                else:
+                    self._usecorrectpython()
+                if self.options.chg:
+                    assert self._installdir
+                    self._installchg()
 
-            result = runner.run(suite)
+                result = runner.run(suite)
 
             if result.failures:
                 failed = True

tests/test-run-tests.t

@@ -224,6 +224,60 b' test --xunit support'
   test-failure-unicode.t * (glob)
   test-failure.t * (glob)
   test-success.t * (glob)
+
+  $ rt --list-tests
+  test-failure-unicode.t
+  test-failure.t
+  test-success.t
+
+  $ rt --list-tests --json
+  test-failure-unicode.t
+  test-failure.t
+  test-success.t
+  $ cat report.json
+  testreport ={
+      "test-failure-unicode.t": {
+          "result": "success"
+      },
+      "test-failure.t": {
+          "result": "success"
+      },
+      "test-success.t": {
+          "result": "success"
+      }
+  } (no-eol)
+
+  $ rt --list-tests --xunit=xunit.xml
+  test-failure-unicode.t
+  test-failure.t
+  test-success.t
+  $ cat xunit.xml
+  <?xml version="1.0" encoding="utf-8"?>
+  <testsuite errors="0" failures="0" name="run-tests" skipped="0" tests="0">
+    <testcase name="test-failure-unicode.t"/>
+    <testcase name="test-failure.t"/>
+    <testcase name="test-success.t"/>
+  </testsuite>
+
+  $ rt --list-tests test-failure* --json --xunit=xunit.xml
+  test-failure-unicode.t
+  test-failure.t
+  $ cat report.json
+  testreport ={
+      "test-failure-unicode.t": {
+          "result": "success"
+      },
+      "test-failure.t": {
+          "result": "success"
+      }
+  } (no-eol)
+  $ cat xunit.xml
+  <?xml version="1.0" encoding="utf-8"?>
+  <testsuite errors="0" failures="0" name="run-tests" skipped="0" tests="0">
+    <testcase name="test-failure-unicode.t"/>
+    <testcase name="test-failure.t"/>
+  </testsuite>
+
   $ rm test-failure-unicode.t
 
 test for --retest