[PATCH v4 03/11] git-p4: add new helper functions for python3 conversion

["Ben Keene via GitGitGadget" <gitgitgadget@gmail.com>]

From: Ben Keene <seraphire@gmail.com>

Python 3+ handles strings differently than Python 2.7.  Since Python 2 is reaching it's end of life, a series of changes are being submitted to enable python 3.7+ support. The current code fails basic tests under python 3.7.

Change the existing unicode test add new support functions for python2-python3 support.

Define the following variables:
- isunicode - a boolean variable that states if the version of python natively supports unicode (true) or not (false). This is true for Python3 and false for Python2.
- unicode - a type alias for the datatype that holds a unicode string.  It is assigned to a str under python 3 and the unicode type for Python2.
- bytes - a type alias for an array of bytes.  It is assigned the native bytes type for Python3 and str for Python2.

Add the following new functions:

- as_string(text) - A new function that will convert a byte array to a unicode (UTF-8) string under python 3.  Under python 2, this returns the string unchanged.
- as_bytes(text) - A new function that will convert a unicode string to a byte array under python 3.  Under python 2, this returns the string unchanged.
- to_unicode(text) - Converts a text string as Unicode(UTF-8) on both Python2 and Python3.

Add a new function alias raw_input:
If raw_input does not exist (it was renamed to input in python 3) alias input as raw_input.

The AS_STRING and AS_BYTES functions allow for modifying the code with a minimal amount of impact on Python2 support.  When a string is expected, the as_string() will be used to convert "cast" the incoming "bytes" to a string type. Conversely as_bytes() will be used to convert a "string" to a "byte array" type. Since Python2 overloads the datatype 'str' to serve both purposes, the Python2 versions of these function do not change the data, since the str functions as both a byte array and a string.

basestring is removed since its only references are found in tests that were changed in the previous change list.

Signed-off-by: Ben Keene <seraphire@gmail.com>
(cherry picked from commit 7921aeb3136b07643c1a503c2d9d8b5ada620356)
---
 git-p4.py | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 66 insertions(+), 4 deletions(-)

diff --git a/git-p4.py b/git-p4.py
index 0f27996393..93dfd0920a 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -32,16 +32,78 @@
     unicode = unicode
 except NameError:
     # 'unicode' is undefined, must be Python 3
-    str = str
+    #
+    # For Python3 which is natively unicode, we will use 
+    # unicode for internal information but all P4 Data
+    # will remain in bytes
+    isunicode = True
     unicode = str
     bytes = bytes
-    basestring = (str,bytes)
+
+    def as_string(text):
+        """Return a byte array as a unicode string"""
+        if text == None:
+            return None
+        if isinstance(text, bytes):
+            return unicode(text, "utf-8")
+        else:
+            return text
+
+    def as_bytes(text):
+        """Return a Unicode string as a byte array"""
+        if text == None:
+            return None
+        if isinstance(text, bytes):
+            return text
+        else:
+            return bytes(text, "utf-8")
+
+    def to_unicode(text):
+        """Return a byte array as a unicode string"""
+        return as_string(text)    
+
+    def path_as_string(path):
+        """ Converts a path to the UTF8 encoded string """
+        if isinstance(path, unicode):
+            return path
+        return encodeWithUTF8(path).decode('utf-8')
+    
 else:
     # 'unicode' exists, must be Python 2
-    str = str
+    #
+    # We will treat the data as:
+    #   str   -> str
+    #   bytes -> str
+    # So for Python2 these functions are no-ops
+    # and will leave the data in the ambiguious
+    # string/bytes state
+    isunicode = False
     unicode = unicode
     bytes = str
-    basestring = basestring
+
+    def as_string(text):
+        """ Return text unaltered (for Python3 support) """
+        return text
+
+    def as_bytes(text):
+        """ Return text unaltered (for Python3 support) """
+        return text
+
+    def to_unicode(text):
+        """Return a string as a unicode string"""
+        return text.decode('utf-8')
+    
+    def path_as_string(path):
+        """ Converts a path to the UTF8 encoded bytes """
+        return encodeWithUTF8(path)
+
+
+ 
+# Check for raw_input support
+try:
+    raw_input
+except NameError:
+    raw_input = input
 
 try:
     from subprocess import CalledProcessError
-- 
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