MSVS_CACHE: Reword the CHANGES and RELEASE entries

Sharpened up the descriptions of the change in PR 4111.
Changed the opening of the cache file to use pathlib functions.

Signed-off-by: Mats Wichmann <mats@linux.com>

3 files changed, 26 insertions, 16 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index e7be169..41b02d9 100755
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -57,11 +57,14 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Fixed crash in C scanner's dictify_CPPDEFINES() function which happens if
       AppendUnique is called on CPPPATH. (Issue #4108).
     - The MSVC script_env_cache now contains a sanity check: if the retrieved
-      tools path does not exist, it is invalidated so it will be recomputed.
-      The dictionary key, which is the name of a batch file, is also computed
-      a bit differently: the dashes are left off if there are no arguments.
-      The cachefile is changed to have a .json suffix, for better recognition
-      on Windows where there might, for example, be an editor association.
+      tools path does not exist, the entry is invalidated so it will
+      be recomputed, in an attempt to avoid scons failing when certain
+      compiler version bumps have taken place.  The dictionary key (uses
+      the name of a batch file and any arguments which may have been
+      passes), is now computed a bit differently: the dashes are left
+      off if there are no arguments.  The default cachefile is changed
+      to have a .json suffix, for better recognition on Windows since
+      the contents are json.
 
   From Zhichang Yu:
     - Added MSVC_USE_SCRIPT_ARGS variable to pass arguments to MSVC_USE_SCRIPT.
diff --git a/RELEASE.txt b/RELEASE.txt
index 80b8bf1..c021a40 100755
--- a/RELEASE.txt
+++ b/RELEASE.txt
@@ -26,19 +26,23 @@ CHANGED/ENHANCED EXISTING FUNCTIONALITY
 ---------------------------------------
 
 - On Windows, %AllUsersProfile%\scons\site_scons is now the default "system"
-  location for a site_scons. %AllUsersProfile%\Application Data\scons\site_scons
-  will continue to work. There does not seem to be any convention to use
-  an "Application Data" subdirectory here.
+  location for a site_scons directory.
+  %AllUsersProfile%\Application Data\scons\site_scons will continue to work.
+  There does not seem to be any existing convention to use an
+  "Application Data" subdirectory here.
 - Action._subproc() can now be used as a python context manager to ensure that the
   POpen object is properly closed.
-- SCons help (-H) no longer prints the "ignored for compatibility" options,
-  which are still listed in the manpage.
+- SCons help (-H) no longer prints the "ignored for compatibility" options
+  to save some space (these are still listed in the manpage).
 - The change to "content" and "content-timestamp" Decider names is reflected
   in the User Guide as well, since the hash function may be other than md5
   (tidying up from earlier change)
-- The SCONS_CACHE_MSVC_CONFIG behavior changes slightly: will now do a
-  sanity check to hopefully regenerate if the compiler version has changed,
-  rather than fail; the default filename now has a .json suffix.
+- If SCONS_CACHE_MSVC_CONFIG is used, it will now attempt a sanity check for
+  the cached compiler information, and regenerate the information
+  if needed, rather than just failing after certain compiler version
+  changes have  happened.  The cache file can still be manually removed
+  if there are issues to force a regen.  The default cache filename now
+  has a .json suffix - the contents have always been json.
 
 
 FIXES
diff --git a/SCons/Tool/MSCommon/common.py b/SCons/Tool/MSCommon/common.py
index fee460a..16ed42c 100644
--- a/SCons/Tool/MSCommon/common.py
+++ b/SCons/Tool/MSCommon/common.py
@@ -31,6 +31,7 @@ import os
 import re
 import subprocess
 import sys
+from pathlib import Path
 
 import SCons.Util
 
@@ -102,7 +103,8 @@ def read_script_env_cache():
     envcache = {}
     if CONFIG_CACHE:
         try:
-            with open(CONFIG_CACHE, 'r') as f:
+            p = Path(CONFIG_CACHE)
+            with p.open('r') as f:
                 envcache = json.load(f)
         except FileNotFoundError:
             # don't fail if no cache file, just proceed without it
@@ -114,11 +116,12 @@ def write_script_env_cache(cache):
     """ write out cache of msvc env vars if requested """
     if CONFIG_CACHE:
         try:
-            with open(CONFIG_CACHE, 'w') as f:
+            p = Path(CONFIG_CACHE)
+            with p.open('w') as f:
                 json.dump(cache, f, indent=2)
         except TypeError:
             # data can't serialize to json, don't leave partial file
-            os.remove(CONFIG_CACHE)
+            p.unlink(missing_ok=True)
         except IOError:
             # can't write the file, just skip
             pass