Merge pull request #3218 from mwichmann/script-paths

Get a little smarter about finding the scons engine.

3 files changed, 98 insertions, 90 deletions

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index 9b3eec4..56127ae 100644
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -160,6 +160,7 @@ RELEASE 3.1.0.alpha.yyyymmdd - NEW DATE WILL BE INSERTED HERE
     - Add xz compression format to packaging choices.
     - Syntax cleanups - trailing blanks, use "is" to compare with None, etc.
       Three uses of variables not defined are changed.
+    - Some script changes in trying to find scons engine
 
   From Hao Wu
     - typo in customized decider example in user guide
diff --git a/src/script/scons.py b/src/script/scons.py
index f2a44f8..d22e76b 100644
--- a/src/script/scons.py
+++ b/src/script/scons.py
@@ -37,10 +37,18 @@ __date__ = "__DATE__"
 
 __developer__ = "__DEVELOPER__"
 
+# This is the entry point to the SCons program.
+# The only job of this script is to work out where the guts of the program
+# could be and import them, where the real work begins.
+# SCons can be invoked several different ways
+# - from an installed location
+# - from a "local install" copy
+# - from a source tree, which has a different dir struture than the other two
+# Try to account for all those possibilities.
+
 import os
 import sys
 
-
 ##############################################################################
 # BEGIN STANDARD SCons SCRIPT HEADER
 #
@@ -50,57 +58,53 @@ import sys
 # should also change other scripts that use this same header.
 ##############################################################################
 
-# Strip the script directory from sys.path() so on case-insensitive
-# (WIN32) systems Python doesn't think that the "scons" script is the
-# "SCons" package.  Replace it with our own library directories
-# (version-specific first, in case they installed by hand there,
-# followed by generic) so we pick up the right version of the build
-# engine modules if they're in either directory.
-
-
+# compatibility check
 if (3,0,0) < sys.version_info < (3,5,0) or sys.version_info < (2,7,0):
     msg = "scons: *** SCons version %s does not run under Python version %s.\n\
-Python < 3.5 is not yet supported.\n"
+Python 2.7 or >= 3.5 is required.\n"
     sys.stderr.write(msg % (__version__, sys.version.split()[0]))
     sys.exit(1)
 
-
-script_dir = os.path.dirname(os.path.realpath(__file__))
-
-if script_dir in sys.path:
-    sys.path.remove(script_dir)
+# Strip the script directory from sys.path so on case-insensitive
+# (WIN32) systems Python doesn't think that the "scons" script is the
+# "SCons" package.
+script_dir = os.path.dirname(__file__)
+script_path = os.path.realpath(os.path.dirname(__file__))
+if script_path in sys.path:
+    sys.path.remove(script_path)
 
 libs = []
 
 if "SCONS_LIB_DIR" in os.environ:
     libs.append(os.environ["SCONS_LIB_DIR"])
 
-# - running from source takes priority (since 2.3.2), excluding SCONS_LIB_DIR settings
-script_path = os.path.abspath(os.path.dirname(__file__))
-source_path = os.path.join(script_path, '..', 'engine')
-libs.append(source_path)
+# running from source takes 2nd priority (since 2.3.2), following SCONS_LIB_DIR
+source_path = os.path.join(script_path, os.pardir, 'engine')
+if os.path.isdir(source_path):
+    libs.append(source_path)
 
+# add local-install locations
 local_version = 'scons-local-' + __version__
 local = 'scons-local'
 if script_dir:
     local_version = os.path.join(script_dir, local_version)
     local = os.path.join(script_dir, local)
-libs.append(os.path.abspath(local_version))
-libs.append(os.path.abspath(local))
+if os.path.isdir(local_version):
+    libs.append(os.path.abspath(local_version))
+if os.path.isdir(local):
+    libs.append(os.path.abspath(local))
 
 scons_version = 'scons-%s' % __version__
 
 # preferred order of scons lookup paths
 prefs = []
 
-
-# - running from egg check
+# if we can find package information, use it
 try:
     import pkg_resources
 except ImportError:
     pass
 else:
-    # when running from an egg add the egg's directory
     try:
         d = pkg_resources.get_distribution('scons')
     except pkg_resources.DistributionNotFound:
@@ -109,18 +113,18 @@ else:
         prefs.append(d.location)
 
 if sys.platform == 'win32':
-    # sys.prefix is (likely) C:\Python*;
-    # check only C:\Python*.
+    # Use only sys.prefix on Windows
     prefs.append(sys.prefix)
     prefs.append(os.path.join(sys.prefix, 'Lib', 'site-packages'))
 else:
     # On other (POSIX) platforms, things are more complicated due to
-    # the variety of path names and library locations.  Try to be smart
-    # about it.
+    # the variety of path names and library locations.
+    # Build up some possibilities, then transform them into candidates
+    temp = []
     if script_dir == 'bin':
         # script_dir is `pwd`/bin;
         # check `pwd`/lib/scons*.
-        prefs.append(os.getcwd())
+        temp.append(os.getcwd())
     else:
         if script_dir == '.' or script_dir == '':
             script_dir = os.getcwd()
@@ -128,42 +132,41 @@ else:
         if tail == "bin":
             # script_dir is /foo/bin;
             # check /foo/lib/scons*.
-            prefs.append(head)
+            temp.append(head)
 
     head, tail = os.path.split(sys.prefix)
     if tail == "usr":
         # sys.prefix is /foo/usr;
         # check /foo/usr/lib/scons* first,
         # then /foo/usr/local/lib/scons*.
-        prefs.append(sys.prefix)
-        prefs.append(os.path.join(sys.prefix, "local"))
+        temp.append(sys.prefix)
+        temp.append(os.path.join(sys.prefix, "local"))
     elif tail == "local":
         h, t = os.path.split(head)
         if t == "usr":
             # sys.prefix is /foo/usr/local;
             # check /foo/usr/local/lib/scons* first,
             # then /foo/usr/lib/scons*.
-            prefs.append(sys.prefix)
-            prefs.append(head)
+            temp.append(sys.prefix)
+            temp.append(head)
         else:
             # sys.prefix is /foo/local;
             # check only /foo/local/lib/scons*.
-            prefs.append(sys.prefix)
+            temp.append(sys.prefix)
     else:
         # sys.prefix is /foo (ends in neither /usr or /local);
         # check only /foo/lib/scons*.
-        prefs.append(sys.prefix)
+        temp.append(sys.prefix)
+
+    # suffix these to add to our original prefs:
+    prefs.extend([os.path.join(x, 'lib') for x in temp])
+    prefs.extend([os.path.join(x, 'lib', 'python' + sys.version[:3],
+                               'site-packages') for x in temp])
 
-    temp = [os.path.join(x, 'lib') for x in prefs]
-    temp.extend([os.path.join(x,
-                                           'lib',
-                                           'python' + sys.version[:3],
-                                           'site-packages') for x in prefs])
-    prefs = temp
 
     # Add the parent directory of the current python's library to the
-    # preferences.  On SuSE-91/AMD64, for example, this is /usr/lib64,
-    # not /usr/lib.
+    # preferences.  This picks up differences between, e.g., lib and lib64,
+    # and finds the base location in case of a non-copying virtualenv.
     try:
         libpath = os.__file__
     except AttributeError:
@@ -177,9 +180,9 @@ else:
         prefs.append(libpath)
 
 # Look first for 'scons-__version__' in all of our preference libs,
-# then for 'scons'.
-libs.extend([os.path.join(x, scons_version) for x in prefs])
-libs.extend([os.path.join(x, 'scons') for x in prefs])
+# then for 'scons'.  Skip paths that do not exist.
+libs.extend([os.path.join(x, scons_version) for x in prefs if os.path.isdir(x)])
+libs.extend([os.path.join(x, 'scons') for x in prefs if os.path.isdir(x)])
 
 sys.path = libs + sys.path
 
@@ -191,9 +194,9 @@ if __name__ == "__main__":
     try:
         import SCons.Script
     except ImportError:
-        print("SCons import failed. Unable to find engine files in:")
+        sys.stderr.write("SCons import failed. Unable to find engine files in:\n")
         for path in libs:
-            print("  {}".format(path))
+            sys.stderr.write("  {}\n".format(path))
         raise
 
     # this does all the work, and calls sys.exit
diff --git a/src/script/sconsign.py b/src/script/sconsign.py
index 559dffe..2337f67 100644
--- a/src/script/sconsign.py
+++ b/src/script/sconsign.py
@@ -49,48 +49,53 @@ import sys
 # should also change other scripts that use this same header.
 ##############################################################################
 
-# Strip the script directory from sys.path() so on case-insensitive
+# compatibility check
+if (3,0,0) < sys.version_info < (3,5,0) or sys.version_info < (2,7,0):
+    msg = "scons: *** SCons version %s does not run under Python version %s.\n\
+Python 2.7 or >= 3.5 is required.\n"
+    sys.stderr.write(msg % (__version__, sys.version.split()[0]))
+    sys.exit(1)
+
+# Strip the script directory from sys.path so on case-insensitive
 # (WIN32) systems Python doesn't think that the "scons" script is the
-# "SCons" package.  Replace it with our own library directories
-# (version-specific first, in case they installed by hand there,
-# followed by generic) so we pick up the right version of the build
-# engine modules if they're in either directory.
-
-
-script_dir = os.path.dirname(os.path.realpath(__file__))
-
-if script_dir in sys.path:
-    sys.path.remove(script_dir)
+# "SCons" package.
+script_dir = os.path.dirname(__file__)
+script_path = os.path.realpath(os.path.dirname(__file__))
+if script_path in sys.path:
+    sys.path.remove(script_path)
 
 libs = []
 
 if "SCONS_LIB_DIR" in os.environ:
     libs.append(os.environ["SCONS_LIB_DIR"])
 
-# - running from source takes priority (since 2.3.2), excluding SCONS_LIB_DIR settings
-script_path = os.path.abspath(os.path.dirname(__file__))
-source_path = os.path.join(script_path, '..', 'engine')
-libs.append(source_path)
+# running from source takes 2nd priority (since 2.3.2), following SCONS_LIB_DIR
+source_path = os.path.join(script_path, os.pardir, 'engine')
+if os.path.isdir(source_path):
+    libs.append(source_path)
 
+# add local-install locations
 local_version = 'scons-local-' + __version__
 local = 'scons-local'
 if script_dir:
     local_version = os.path.join(script_dir, local_version)
     local = os.path.join(script_dir, local)
-libs.append(os.path.abspath(local_version))
-libs.append(os.path.abspath(local))
+if os.path.isdir(local_version):
+    libs.append(os.path.abspath(local_version))
+if os.path.isdir(local):
+    libs.append(os.path.abspath(local))
 
 scons_version = 'scons-%s' % __version__
 
 # preferred order of scons lookup paths
 prefs = []
 
+# if we can find package information, use it
 try:
     import pkg_resources
 except ImportError:
     pass
 else:
-    # when running from an egg add the egg's directory
     try:
         d = pkg_resources.get_distribution('scons')
     except pkg_resources.DistributionNotFound:
@@ -99,18 +104,18 @@ else:
         prefs.append(d.location)
 
 if sys.platform == 'win32':
-    # sys.prefix is (likely) C:\Python*;
-    # check only C:\Python*.
+    # Use only sys.prefix on Windows
     prefs.append(sys.prefix)
     prefs.append(os.path.join(sys.prefix, 'Lib', 'site-packages'))
 else:
     # On other (POSIX) platforms, things are more complicated due to
-    # the variety of path names and library locations.  Try to be smart
-    # about it.
+    # the variety of path names and library locations.
+    # Build up some possibilities, then transform them into candidates
+    temp = []
     if script_dir == 'bin':
         # script_dir is `pwd`/bin;
         # check `pwd`/lib/scons*.
-        prefs.append(os.getcwd())
+        temp.append(os.getcwd())
     else:
         if script_dir == '.' or script_dir == '':
             script_dir = os.getcwd()
@@ -118,42 +123,41 @@ else:
         if tail == "bin":
             # script_dir is /foo/bin;
             # check /foo/lib/scons*.
-            prefs.append(head)
+            temp.append(head)
 
     head, tail = os.path.split(sys.prefix)
     if tail == "usr":
         # sys.prefix is /foo/usr;
         # check /foo/usr/lib/scons* first,
         # then /foo/usr/local/lib/scons*.
-        prefs.append(sys.prefix)
-        prefs.append(os.path.join(sys.prefix, "local"))
+        temp.append(sys.prefix)
+        temp.append(os.path.join(sys.prefix, "local"))
     elif tail == "local":
         h, t = os.path.split(head)
         if t == "usr":
             # sys.prefix is /foo/usr/local;
             # check /foo/usr/local/lib/scons* first,
             # then /foo/usr/lib/scons*.
-            prefs.append(sys.prefix)
-            prefs.append(head)
+            temp.append(sys.prefix)
+            temp.append(head)
         else:
             # sys.prefix is /foo/local;
             # check only /foo/local/lib/scons*.
-            prefs.append(sys.prefix)
+            temp.append(sys.prefix)
     else:
         # sys.prefix is /foo (ends in neither /usr or /local);
         # check only /foo/lib/scons*.
-        prefs.append(sys.prefix)
+        temp.append(sys.prefix)
+
+    # suffix these to add to our original prefs:
+    prefs.extend([os.path.join(x, 'lib') for x in temp])
+    prefs.extend([os.path.join(x, 'lib', 'python' + sys.version[:3],
+                               'site-packages') for x in temp])
 
-    temp = [os.path.join(x, 'lib') for x in prefs]
-    temp.extend([os.path.join(x,
-                                           'lib',
-                                           'python' + sys.version[:3],
-                                           'site-packages') for x in prefs])
-    prefs = temp
 
     # Add the parent directory of the current python's library to the
-    # preferences.  On SuSE-91/AMD64, for example, this is /usr/lib64,
-    # not /usr/lib.
+    # preferences.  This picks up differences between, e.g., lib and lib64,
+    # and finds the base location in case of a non-copying virtualenv.
     try:
         libpath = os.__file__
     except AttributeError:
@@ -167,9 +171,9 @@ else:
         prefs.append(libpath)
 
 # Look first for 'scons-__version__' in all of our preference libs,
-# then for 'scons'.
-libs.extend([os.path.join(x, scons_version) for x in prefs])
-libs.extend([os.path.join(x, 'scons') for x in prefs])
+# then for 'scons'.  Skip paths that do not exist.
+libs.extend([os.path.join(x, scons_version) for x in prefs if os.path.isdir(x)])
+libs.extend([os.path.join(x, 'scons') for x in prefs if os.path.isdir(x)])
 
 sys.path = libs + sys.path