use templfile instead of incrementing number

Author: DavidSpickett

llvm/utils/lit/lit/cl_arguments.py

@@ -178,12 +178,8 @@ def parse_args():
     execution_group.add_argument(
         "--use-unique-output-file-name",
         help="When enabled, lit will not overwrite existing test report files. "
-        "Instead it will modify the file name until it finds a file name "
-        "that does not already exist. An incrementing number starting from 1 "
-        "will be added prior to the file extension, or for files without an "
-        "extension, on the end of the fle name. For example, if 'results.xml' "
-        "already exists, 'results.1.xml' will be used instead, if that exists, "
-        "'results.2.xml' and so on. [Default: Off]",
+        "Instead it will write to a new file named the same as the output file "
+        "name but with a extra part before the file extension. [Default: Off]",
         action="store_true",
     )
     execution_group.add_argument(

llvm/utils/lit/lit/reports.py

@@ -4,6 +4,7 @@
 import itertools
 import json
 import os
+import tempfile
 
 from xml.sax.saxutils import quoteattr as quo
 
@@ -24,19 +25,11 @@ def __init__(self, output_file):
 
     def write_results(self, tests, elapsed):
         if self.use_unique_output_file_name:
-            report_file = None
-            filepath = self.output_file
-            attempt = 0
-            while report_file is None:
-                try:
-                    report_file = open(filepath, "x")
-                except FileExistsError:
-                    attempt += 1
-                    # If there is an extension insert before that because most
-                    # glob patterns for these will be '*.extension'. Otherwise
-                    # add to the end of the path.
-                    path, ext = os.path.splitext(self.output_file)
-                    filepath = path + f".{attempt}" + ext
+            filename, ext = os.path.splitext(os.path.basename(self.output_file))
+            fd, _ = tempfile.mkstemp(
+                suffix=ext, prefix=f"{filename}.", dir=os.path.dirname(self.output_file)
+            )
+            report_file = os.fdopen(fd, "w")
         else:
             # Overwrite if the results already exist.
             report_file = open(self.output_file, "w")

llvm/utils/lit/tests/unique-output-file.py

@@ -6,21 +6,15 @@
 # RUN: echo "test" > %t.xunit.xml
 # RUN: not %{lit} --xunit-xml-output %t.xunit.xml %{inputs}/xunit-output
 # RUN: FileCheck < %t.xunit.xml %s --check-prefix=NEW
+# NEW:      <?xml version="1.0" encoding="UTF-8"?>
+# NEW-NEXT: <testsuites time="{{[0-9.]+}}">
+## (other tests will check the contents of the whole file)
 
 # RUN: rm -f %t.xunit*.xml
 # RUN: echo "test" > %t.xunit.xml
 ## Files should not be overwritten with the option.
 # RUN: not %{lit} --xunit-xml-output %t.xunit.xml --use-unique-output-file-name %{inputs}/xunit-output
 # RUN: FileCheck < %t.xunit.xml %s --check-prefix=EXISTING
 # EXISTING: test
-## Results in a new file with "1" added.
-# RUN: FileCheck < %t.xunit.1.xml %s --check-prefix=NEW
-# NEW:      <?xml version="1.0" encoding="UTF-8"?>
-# NEW-NEXT: <testsuites time="{{[0-9.]+}}">
-## (assuming that other tests check the whole contents of the file)
-
-## The number should increment as many times as needed.
-# RUN: touch %t.xunit.2.xml %t.xunit.3.xml %t.xunit.4.xml
-
-# RUN: not %{lit} --xunit-xml-output %t.xunit.xml --use-unique-output-file-name %{inputs}/xunit-output
-# RUN: FileCheck < %t.xunit.5.xml %s --check-prefix=NEW
+## Results in a new file with some discriminator added.
+# RUN: FileCheck < %t.xunit.*.xml %s --check-prefix=NEW