[benchmark] Add script to automate creation of new single-source benchmarks

Adds a `create_benchmark` script that automates the following three tasks:
1. Add a new Swift file (YourTestNameHere.swift), built according to the template below, to the {{single-source}}directory.
2. Add the filename of the new Swift file to CMakeLists.txt
3. Edit main.swift. Import and register your new Swift module.

The process of adding new benchmarks is now automated and a lot less error-prone.

Author: BalestraPatrick

benchmark/scripts/create_benchmark.py

@@ -0,0 +1,141 @@
+#!/usr/bin/env python
+
+import argparse
+import os
+import re
+
+benchmark_template = """//===--- {name}.swift -------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import TestsUtils
+
+public let {name} = [
+  BenchmarkInfo(name: "{name}", runFunction: run_{name}, tags: [.validation, .api]),
+]
+
+@inline(never)
+public func run_{name}(N: Int) {{
+    // TODO
+}}"""
+
+def main():
+    p = argparse.ArgumentParser()
+    p.add_argument('name', help='The name of the new benchmark to be created')
+    args = p.parse_args()
+
+    # adds benchmark to `CMakeLists.txt`
+    update_cmakelists(args.name)
+    # create benchmark Swift file
+    create_benchmark_file(args.name)
+    # imports the benchmark module in `main.swift`
+    add_import_benchmark(args.name)
+    # registers the benchmark with the driver in `main.swift`
+    add_register_benchmark(args.name)
+
+def update_cmakelists(name):
+    """Adds a new entry to the `CMakeLists.txt` file with the given benchmark name."""
+    relative_path = create_relative_path('../CMakeLists.txt')
+
+    file_contents = []
+    with open(relative_path, 'r') as f:
+        file_contents = f.readlines()
+
+    file_new_contents = insert_line_alphabetically(name, '    single-source/' + name + '\n', file_contents, r"    single-source\/([a-zA-Z]+)")
+    with open(relative_path, 'w') as f:
+        for line in file_new_contents:
+            f.write(line)
+
+def create_benchmark_file(name):
+    """Creates a new Swift file with the given name based on the template and places it in the `single-source` directory."""
+    relative_path = create_relative_path('../single-source/')
+    
+    formatted_template = benchmark_template.format(name=name)
+    source_file_path = os.path.join(relative_path, name + '.swift')
+    with open(source_file_path, 'w') as f:
+        f.write(formatted_template)
+
+def add_import_benchmark(name):
+    """Adds an `import` statement to the `main.swift` file for the new benchmark."""
+    relative_path = create_relative_path('../utils/main.swift')
+
+    # read current contents into an array
+    file_contents = []
+    with open(relative_path, 'r') as f:
+        file_contents = f.readlines()
+
+    inserted = False
+    # the test dependencies are placed before all benchmarks, so we have to insert the benchmark in the right alphabetical order after we have seen all test dependencies.
+    read_test_dependencies = False
+    previous_benchmark_name = None
+    file_new_contents = []
+    for line in file_contents:
+        # check if this line is a definition of a benchmark and get its name
+        match = re.search(r"import ([a-zA-Z]+)", line)
+        if match and match.group(1):
+            benchmark_name = match.group(1)
+            # find where to insert the new benchmark in the right alphabetical order
+            if (name < benchmark_name and previous_benchmark_name == None) or (name < benchmark_name and name > previous_benchmark_name):
+                if read_test_dependencies:
+                    file_new_contents.append('import ' + name + '\n' + line)
+                else:
+                    # all test dependencies are first specified, so from now on we can look where to insert the new benchmark.
+                    read_test_dependencies = True
+                    file_new_contents.append(line)
+            else:
+                file_new_contents.append(line)    
+            previous_benchmark_name = benchmark_name
+        else:
+            file_new_contents.append(line)
+    
+    with open(relative_path, 'w') as f:
+        for line in file_new_contents:
+            f.write(line)
+
+def add_register_benchmark(name):
+    """Adds an `import` statement to the `main.swift` file for the new benchmark."""
+    relative_path = create_relative_path('../utils/main.swift')
+
+    file_contents = []
+    with open(relative_path, 'r') as f:
+        file_contents = f.readlines()
+
+    file_new_contents = insert_line_alphabetically(name, 'registerBenchmark(' + name + ')\n', file_contents, r"registerBenchmark\(([a-zA-Z]+)\)")
+    with open(relative_path, 'w') as f:
+        for line in file_new_contents:
+            f.write(line)
+
+def insert_line_alphabetically(name, new_line, lines, regex):
+    """Iterates through the given lines and executes the regex on each line to find where the new benchmark should be inserted with the given `new_line`."""
+    # the name of the previous seen benchmark in order to insert the new one at the correct position 
+    previous_benchmark_name = None
+    # the new contents of the file
+    updated_lines = []
+    for line in lines:
+        # apply regex and get name of benchmark on this line
+        match = re.search(regex, line)
+        if match and match.group(1):
+            benchmark_name = match.group(1)
+            # check if we're at the line where we have to insert the new benchmark in the correct alphabetical order
+            if (name < benchmark_name and previous_benchmark_name == None) or (name < benchmark_name and name > previous_benchmark_name):
+                updated_lines.append(new_line + line)
+            else:
+                updated_lines.append(line)    
+            previous_benchmark_name = benchmark_name
+        else:
+            updated_lines.append(line)
+    return updated_lines
+
+def create_relative_path(file_path):
+    return os.path.join(os.path.dirname(__file__), file_path)
+
+if __name__ == "__main__":
+    main()