gyp: improve Windows+Cygwin compatibility

Fixes: #1782
PR-URL: https://github.com/nodejs/node-gyp/pull/1817
Reviewed-By: Christian Clauss <cclauss@me.com>
Reviewed-By: Rod Vagg <r@va.gg>

gyp/gyp_main.py

@@ -6,10 +6,38 @@
 
 import os
 import sys
+import subprocess
+
+# Below IsCygwin() function copied from pylib/gyp/common.py
+def IsCygwin():
+  try:
+    out = subprocess.Popen("uname",
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT)
+    stdout,stderr = out.communicate()
+    return "CYGWIN" in str(stdout)
+  except Exception:
+    return False
+
+
+def UnixifyPath(path):
+  try:
+    if not IsCygwin():
+      return path
+    out = subprocess.Popen(["cygpath", "-u", path],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT)
+    stdout,stderr = out.communicate()
+    return str(stdout)
+  except Exception:
+    return path
+
 
 # Make sure we're using the version of pylib in this repo, not one installed
-# elsewhere on the system.
-sys.path.insert(0, os.path.join(os.path.dirname(sys.argv[0]), 'pylib'))
+# elsewhere on the system. Also convert to Unix style path on Cygwin systems,
+# else the 'gyp' library will not be found
+path = UnixifyPath(sys.argv[0])
+sys.path.insert(0, os.path.join(os.path.dirname(path), 'pylib'))
 import gyp
 
 if __name__ == '__main__':

gyp/pylib/gyp/common.py

@@ -9,6 +9,7 @@ import os.path
 import re
 import tempfile
 import sys
+import subprocess
 
 
 # A minimal memoizing decorator. It'll blow up if the args aren't immutable,
@@ -337,11 +338,16 @@ def WriteOnDiff(filename):
   class Writer(object):
     """Wrapper around file which only covers the target if it differs."""
     def __init__(self):
+      # On Cygwin remove the "dir" argument because `C:` prefixed paths are treated as relative,
+      # consequently ending up with current dir "/cygdrive/c/..." being prefixed to those, which was
+      # obviously a non-existent path, for example: "/cygdrive/c/<some folder>/C:\<my win style abs path>".
+      # See https://docs.python.org/2/library/tempfile.html#tempfile.mkstemp for more details
+      base_temp_dir = "" if IsCygwin() else os.path.dirname(filename)
       # Pick temporary file.
       tmp_fd, self.tmp_path = tempfile.mkstemp(
           suffix='.tmp',
           prefix=os.path.split(filename)[1] + '.gyp.',
-          dir=os.path.split(filename)[0])
+          dir=base_temp_dir)
       try:
         self.tmp_file = os.fdopen(tmp_fd, 'wb')
       except Exception:
@@ -611,3 +617,14 @@ def CrossCompileRequested():
           os.environ.get('AR_target') or
           os.environ.get('CC_target') or
           os.environ.get('CXX_target'))
+
+def IsCygwin():
+  try:
+    out = subprocess.Popen("uname",
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT)
+    stdout,stderr = out.communicate()
+    return "CYGWIN" in str(stdout)
+  except Exception:
+    return False
+

gyp/pylib/gyp/generator/msvs.py

@@ -165,7 +165,7 @@ def _FixPath(path):
   Returns:
     The path with all slashes made into backslashes.
   """
-  if fixpath_prefix and path and not os.path.isabs(path) and not path[0] == '$':
+  if fixpath_prefix and path and not os.path.isabs(path) and not path[0] == '$' and not _IsWindowsAbsPath(path):
     path = os.path.join(fixpath_prefix, path)
   path = path.replace('/', '\\')
   path = _NormalizedSource(path)
@@ -174,6 +174,16 @@ def _FixPath(path):
   return path
 
 
+def _IsWindowsAbsPath(path):
+  """
+  On Cygwin systems Python needs a little help determining if a path is an absolute Windows path or not, so that
+  it does not treat those as relative, which results in bad paths like:
+
+  '..\C:\<some path>\some_source_code_file.cc'
+  """
+  return path.startswith('c:') or path.startswith('C:')
+
+
 def _FixPaths(paths):
   """Fix each of the paths of the list."""
   return [_FixPath(i) for i in paths]