Don't write ApprovalTests' temporary files into the source tree

This has two effects:
 1) This significantly improves the performance of ApprovalTests
    run in WSL, because running the massively multi-reporter
    test would cause lots of small and parallel writes across the
    WSL-Windows FS boundary, completely mudering performance.

 2) ApprovalTests can be run from multiple build dirs in parallel,
    as long as they do not fail. However, if they do fail,
    the multiple runs will still step on each other toes when
    writing the unapproved files for user.

tests/CMakeLists.txt

@@ -343,7 +343,14 @@ set_tests_properties(FilteredSection::GeneratorsDontCauseInfiniteLoop-2
 )
 
 # AppVeyor has a Python 2.7 in path, but doesn't have .py files as autorunnable
-add_test(NAME ApprovalTests COMMAND ${PYTHON_EXECUTABLE} ${CATCH_DIR}/tools/scripts/approvalTests.py $<TARGET_FILE:SelfTest>)
+add_test(NAME ApprovalTests
+  COMMAND
+    ${PYTHON_EXECUTABLE}
+    ${CATCH_DIR}/tools/scripts/approvalTests.py
+    $<TARGET_FILE:SelfTest>
+    "${CMAKE_CURRENT_BINARY_DIR}"
+)
+
 set_tests_properties(ApprovalTests
   PROPERTIES
     FAIL_REGULAR_EXPRESSION "Results differed"

tools/scripts/approvalTests.py

@@ -8,6 +8,7 @@ import sys
 import subprocess
 import re
 import difflib
+import shutil
 
 import scriptCommon
 from scriptCommon import catchPath
@@ -17,6 +18,35 @@ if os.name == 'nt':
     os.system('')
 
 rootPath = os.path.join(catchPath, 'tests/SelfTest/Baselines')
+# Init so it is guaranteed to fail loudly if the scoping gets messed up
+outputDirPath = None
+
+if len(sys.argv) == 3:
+    cmdPath = sys.argv[1]
+    outputDirBasePath = sys.argv[2]
+    outputDirPath = os.path.join(outputDirBasePath, 'ApprovalTests')
+    if not os.path.isdir(outputDirPath):
+        os.mkdir(outputDirPath)
+else:
+    print('Usage: {} path-to-SelfTest-executable path-to-temp-output-dir'.format(sys.argv[0]))
+    exit(1)
+
+
+
+def get_rawResultsPath(baseName):
+    return os.path.join(outputDirPath, '_{0}.tmp'.format(baseName))
+
+def get_baselinesPath(baseName):
+    return os.path.join(rootPath, '{0}.approved.txt'.format(baseName))
+
+def _get_unapprovedPath(path, baseName):
+    return os.path.join(path, '{0}.unapproved.txt'.format(baseName))
+
+def get_filteredResultsPath(baseName):
+    return _get_unapprovedPath(outputDirPath, baseName)
+
+def get_unapprovedResultsPath(baseName):
+    return _get_unapprovedPath(rootPath, baseName)
 
 langFilenameParser = re.compile(r'(.+\.[ch]pp)')
 filelocParser = re.compile(r'''
@@ -50,14 +80,8 @@ sinceEpochParser = re.compile(r'\d+ .+ since epoch')
 # The weird OR is there to always have at least empty string for group 1
 tapTestNumParser = re.compile(r'^((?:not ok)|(?:ok)|(?:warning)|(?:info)) (\d+) -')
 
-if len(sys.argv) == 2:
-    cmdPath = sys.argv[1]
-else:
-    cmdPath = os.path.join(catchPath, scriptCommon.getBuildExecutable())
-
 overallResult = 0
 
-
 def diffFiles(fileA, fileB):
     with io.open(fileA, 'r', encoding='utf-8', errors='surrogateescape') as file:
         aLines = [line.rstrip() for line in file.readlines()]
@@ -134,18 +158,6 @@ def filterLine(line, isCompact):
     return line
 
 
-def get_rawResultsPath(baseName):
-    return os.path.join(rootPath, '_{0}.tmp'.format(baseName))
-
-
-def get_baselinesPath(baseName):
-    return os.path.join(rootPath, '{0}.approved.txt'.format(baseName))
-
-
-def get_filteredResultsPath(baseName):
-    return os.path.join(rootPath, '{0}.unapproved.txt'.format(baseName))
-
-
 def run_test(baseName, args):
     args[0:0] = [cmdPath]
     if not os.path.exists(cmdPath):
@@ -174,21 +186,20 @@ def check_outputs(baseName):
     os.remove(rawResultsPath)
     print()
     print(baseName + ":")
-    if os.path.exists(baselinesPath):
-        diffResult = diffFiles(baselinesPath, filteredResultsPath)
-        if diffResult:
-            print('\n'.join(diffResult))
-            print("  \n****************************\n  \033[91mResults differed")
-            if len(diffResult) > overallResult:
-                overallResult = len(diffResult)
-        else:
-            os.remove(filteredResultsPath)
-            print("  \033[92mResults matched")
-        print("\033[0m")
+    if not os.path.exists(baselinesPath):
+        print(  'first approval')
+        overallResult += 1
+        return
+
+    diffResult = diffFiles(baselinesPath, filteredResultsPath)
+    if diffResult:
+        print('\n'.join(diffResult))
+        print("  \n****************************\n  \033[91mResults differed\033[0m")
+        overallResult += 1
+        shutil.move(filteredResultsPath, get_unapprovedResultsPath(baseName))
     else:
-        print("  first approval")
-        if overallResult == 0:
-            overallResult = 1
+        os.remove(filteredResultsPath)
+        print("  \033[92mResults matched\033[0m")
 
 
 def approve(baseName, args):
@@ -205,6 +216,7 @@ base_args = ["--order", "lex", "--rng-seed", "1", "--colour-mode", "none"]
 ## special cases first:
 # Standard console reporter
 approve("console.std", ["~[!nonportable]~[!benchmark]~[approvals] *"] + base_args)
+
 # console reporter, include passes, warn about No Assertions, limit failures to first 4
 approve("console.swa4", ["~[!nonportable]~[!benchmark]~[approvals] *", "-s", "-w", "NoAssertions", "-x", "4"] + base_args)
 
@@ -216,8 +228,8 @@ for reporter in reporters:
     reporter_args = ['-r', reporter]
     approve(filename, common_args + reporter_args)
 
-## All reporters at the same time
 
+## All reporters at the same time
 common_args = ["~[!nonportable]~[!benchmark]~[approvals] *", "-s", "-w", "NoAssertions"] + base_args
 filenames = ['{}.sw.multi'.format(reporter) for reporter in reporters]
 reporter_args = []
@@ -225,6 +237,7 @@ for reporter, filename in zip(reporters, filenames):
     reporter_args += ['-r', '{}::out={}'.format(reporter, get_rawResultsPath(filename))]
 
 run_test("default.sw.multi", common_args + reporter_args)
+
 check_outputs("default.sw.multi")
 for reporter, filename in zip(reporters, filenames):
     check_outputs(filename)
@@ -232,4 +245,4 @@ for reporter, filename in zip(reporters, filenames):
 
 if overallResult != 0:
     print("If these differences are expected, run approve.py to approve new baselines.")
-exit(overallResult)
+    exit(2)