From 9b052ace09a47f14cd59eaf8734a5e6cb1b7e5b8 Mon Sep 17 00:00:00 2001
From: Bert Belder <bertbelder@gmail.com>
Date: Sat, 8 Sep 2018 17:56:19 +0200
Subject: [PATCH] tools/setup: replace generated args.gn unless handcrafted

---
 tools/setup.py      | 78 +++++++++++++++++++++++++++++++++++----------
 tools/setup_test.py | 61 +++++++++++++++++++++++++++++++++++
 tools/test.py       |  2 ++
 3 files changed, 125 insertions(+), 16 deletions(-)
 create mode 100644 tools/setup_test.py

diff --git a/tools/setup.py b/tools/setup.py
index 737f80017f..77aaf95d60 100755
--- a/tools/setup.py
+++ b/tools/setup.py
@@ -2,6 +2,7 @@
 import third_party
 from util import run, root_path, build_path, build_mode
 import os
+import re
 import sys
 from distutils.spawn import find_executable
 
@@ -44,15 +45,55 @@ def write_lastchange():
     # ])
 
 
-def get_gn_args():
+# If this text is found in args.gn, we assume it hasn't been hand edited.
+gn_args_header = [
+    "# This file is automatically generated by tools/setup.py.",
+    "# REMOVE THIS LINE to preserve any changes you make.", ""
+]
+
+
+def gn_args_are_generated(lines):
+    for line in lines:
+        if re.match("^\s*#.*REMOVE THIS LINE", line):
+            return True
+    return False
+
+
+def read_gn_args(args_filename):
+    if not os.path.exists(args_filename):
+        return (None, False)  # No content, not hand edited.
+
+    with open(args_filename) as f:
+        lines = f.read().splitlines()
+        args = [l.strip() for l in lines if not re.match("^\s*(#|$)", l)]
+        hand_edited = not gn_args_are_generated(lines)
+        return (args, hand_edited)
+
+
+def write_gn_args(args_filename, args):
+    assert not gn_args_are_generated(args)  # No header -> hand crafted.
+    lines = gn_args_header + args
+    assert gn_args_are_generated(lines)  # With header -> generated.
+
+    # Ensure the directory where args.gn goes exists.
+    dir = os.path.dirname(args_filename)
+    if not os.path.isdir(dir):
+        os.makedirs(dir)
+
+    with open(args_filename, "w") as f:
+        f.write("\n".join(lines) + "\n")
+
+
+def generate_gn_args(mode):
     out = []
-    if build_mode() == "release":
+    if mode == "release":
         out += ["is_official_build=true"]
-    elif build_mode() == "debug":
+    elif mode == "debug":
         pass
     else:
-        print "Bad mode {}. Use 'release' or 'debug' (default)" % build_mode()
+        print "Bad mode {}. Use 'release' or 'debug' (default)" % mode
         sys.exit(1)
+
     if "DENO_BUILD_ARGS" in os.environ:
         out += os.environ["DENO_BUILD_ARGS"].split()
 
@@ -67,8 +108,6 @@ def get_gn_args():
             tc = "//build_extra/toolchain/win:win_clang_x64"
             out += ['custom_toolchain="%s"' % tc, 'host_toolchain="%s"' % tc]
 
-    print "DENO_BUILD_ARGS:", out
-
     return out
 
 
@@ -76,20 +115,27 @@ def get_gn_args():
 def gn_gen(mode):
     os.environ["DENO_BUILD_MODE"] = mode
 
-    # mkdir $build_path(). We do this so we can write args.gn before running gn gen.
-    if not os.path.isdir(build_path()):
-        os.makedirs(build_path())
-
-    # Rather than using gn gen --args we manually write the args.gn override file.
+    # Rather than using gn gen --args we write directly to the args.gn file.
     # This is to avoid quoting/escaping complications when passing overrides as
     # command-line arguments.
     args_filename = os.path.join(build_path(), "args.gn")
-    if os.path.exists(args_filename):
-        print "Skip writing args file: '%s' already exists." % args_filename
+
+    # Check if args.gn exists, and if it was auto-generated or handcrafted.
+    existing_gn_args, hand_edited = read_gn_args(args_filename)
+
+    # If args.gn wasn't handcrafted, regenerate it.
+    if hand_edited:
+        print "%s: Using gn options from hand edited '%s'." % (mode,
+                                                               args_filename)
+        gn_args = existing_gn_args
     else:
-        gn_args = get_gn_args()
-        with open(args_filename, "w+") as f:
-            f.write("\n".join(gn_args) + "\n")
+        print "%s: Writing gn options to '%s'." % (mode, args_filename)
+        gn_args = generate_gn_args(mode)
+        if gn_args != existing_gn_args:
+            write_gn_args(args_filename, gn_args)
+
+    for line in gn_args:
+        print "  " + line
 
     run([third_party.gn_path, "gen", build_path()],
         env=third_party.google_env())
diff --git a/tools/setup_test.py b/tools/setup_test.py
new file mode 100644
index 0000000000..670bf33dba
--- /dev/null
+++ b/tools/setup_test.py
@@ -0,0 +1,61 @@
+# Copyright 2018 the Deno authors. All rights reserved. MIT license.
+
+import os
+from setup import read_gn_args, write_gn_args
+from shutil import rmtree
+from tempfile import mktemp
+
+
+def read_gn_args_test():
+    # Args file doesn't exist.
+    (args, hand_edited) = read_gn_args("/baddir/hopefully/nonexistent/args.gn")
+    assert args is None
+    assert hand_edited == False
+
+    # Handwritten empty args file.
+    filename = mktemp()
+    with open(filename, "w"):
+        pass
+    (args, hand_edited) = read_gn_args(filename)
+    os.remove(filename)
+    assert args == []
+    assert hand_edited == True
+
+    # Handwritten non-empty args file.
+    expect_args = ['some_number=2', 'another_string="ran/dom#yes"']
+    filename = mktemp()
+    with open(filename, "w") as f:
+        f.write("\n".join(expect_args + ["", "# A comment to be ignored"]))
+    (args, hand_edited) = read_gn_args(filename)
+    os.remove(filename)
+    assert args == expect_args
+    assert hand_edited == True
+
+
+def write_gn_args_test():
+    # Build a nonexistent path; write_gn_args() should call mkdir as needed.
+    dir = mktemp()
+    filename = os.path.join(dir, "args.gn")
+    assert not os.path.exists(dir)
+    assert not os.path.exists(filename)
+    # Write some args.
+    args = ['lalala=42', 'foo_bar_baz="lorem ipsum dolor#amet"']
+    write_gn_args(filename, args)
+    # Directory and args file should now be created.
+    assert os.path.isdir(dir)
+    assert os.path.isfile(filename)
+    # Validate that the right contents were written.
+    (check_args, hand_edited) = read_gn_args(filename)
+    assert check_args == args
+    assert hand_edited == False
+    # Clean up.
+    rmtree(dir)
+
+
+def setup_test():
+    read_gn_args_test()
+    write_gn_args_test()
+
+
+if __name__ == '__main__':
+    setup_test()
diff --git a/tools/test.py b/tools/test.py
index 6e5cb548b9..b8f49cf2b2 100755
--- a/tools/test.py
+++ b/tools/test.py
@@ -4,6 +4,7 @@
 import os
 import sys
 from check_output_test import check_output_test
+from setup_test import setup_test
 from util import executable_suffix, run, build_path
 from unit_tests import unit_tests
 from util_test import util_test
@@ -30,6 +31,7 @@ def main(argv):
     http_server.spawn()
 
     # Internal tools testing
+    setup_test()
     util_test()
 
     test_cc = os.path.join(build_dir, "test_cc" + executable_suffix)