Adjust the final compiler executable search and warning message when setting up the msvc environment.

Changes:
* The search for the msvc compiler executable (cl.exe) no longer inspects the OS system path in certain situations when setting up the msvc environment.
* When the msvc compiler executable is not found during setup of the msvc environment, the warning message issued takes into account whether or not a possibly erroneous compiler executable was already present in the scons environment path.

4 files changed, 32 insertions, 6 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index a55c53249..97924dd6e 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -42,6 +42,13 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
       registry query that returns a path that does not exist.  Multiple invocation
       paths were not prepared to handle the MissingConfiguration exception.  The
       MissingConfiguration exception type was removed.
+    - The detection of the msvc compiler executable (cl.exe) has been modified.  The
+      compiler detection no longer considers the host os environment path.  In addition,
+      existence of the msvc compiler executable is checked in the detection dictionary
+      and the scons ENV path before the detection dictionary is merged into the scons
+      ENV.  Different warnings are produced when the msvc compiler is not detected in the
+      detection dictionary based on whether or not an msvc compiler was detected in the
+      scons ENV path (i.e., already exists in the user's ENV path prior to detection).
 
   From Vitaly Cheptsov:
     - Fix race condition in `Mkdir` which can happen when two `SConscript`
diff --git a/RELEASE.txt b/RELEASE.txt
index 12bb3cacb..94e15238d 100644
--- a/RELEASE.txt
+++ b/RELEASE.txt
@@ -59,6 +59,10 @@ CHANGED/ENHANCED EXISTING FUNCTIONALITY
   batch file exists but an individual msvc toolset may not support the host/target
   architecture combination.  For example, when using VS2022 on arm64, the arm64 native
   tools are only installed for the 14.3x toolsets.
+- MSVC: When the msvc compiler executable is not found during setup of the msvc
+  environment, the warning message issued takes into account whether or not a
+  possibly erroneous compiler executable was already present in the scons environment
+  path.
 - Extend range of recognized Java versions to 20.
 - Builder calls (like Program()) now accept pathlib objects in source lists.
 - The Help() function now takes an additional keyword argument keep_local:
@@ -101,6 +105,8 @@ FIXES
 - MSVC: Erroneous construction of the installed msvc list (as described above) caused an
   index error in the msvc support code.  An explicit check was added to prevent indexing
   into an empty list.  Fixes #4312.
+- MSVC: The search for the msvc compiler executable (cl.exe) no longer inspects the
+  OS system path in certain situations when setting up the msvc environment.
 - MSCommon: Test SConfTests.py would fail when mscommon debugging was enabled via the
   MSVC_MSCOMMON_DEBUG environment variable.  The mscommon logging filter class registered
   with the python logging module was refactored to prevent test failure.
diff --git a/SCons/Tool/MSCommon/vc.py b/SCons/Tool/MSCommon/vc.py
index 56d9c381e..592696056 100644
--- a/SCons/Tool/MSCommon/vc.py
+++ b/SCons/Tool/MSCommon/vc.py
@@ -1515,19 +1515,32 @@ def msvc_setup_env(env):
         SCons.Warnings.warn(SCons.Warnings.VisualCMissingWarning, warn_msg)
         return None
 
+    found_cl_path = None
+    found_cl_envpath = None
+
+    seen_path = False
     for k, v in d.items():
+        if not seen_path and k == 'PATH':
+            seen_path = True
+            found_cl_path = SCons.Util.WhereIs('cl', v)
+            found_cl_envpath = SCons.Util.WhereIs('cl', env['ENV'].get(k, []))
         env.PrependENVPath(k, v, delete_existing=True)
         debug("env['ENV']['%s'] = %s", k, env['ENV'][k])
 
-    # final check to issue a warning if the compiler is not present
-    if not find_program_path(env, 'cl'):
-        debug("did not find %s", _CL_EXE_NAME)
+    debug("cl paths: d['PATH']=%s, ENV['PATH']=%s", repr(found_cl_path), repr(found_cl_envpath))
+
+    # final check to issue a warning if the requested compiler is not present
+    if not found_cl_path:
         if CONFIG_CACHE:
             propose = f"SCONS_CACHE_MSVC_CONFIG caching enabled, remove cache file {CONFIG_CACHE} if out of date."
         else:
             propose = "It may need to be installed separately with Visual Studio."
-        warn_msg = f"Could not find MSVC compiler 'cl'. {propose}"
-        SCons.Warnings.warn(SCons.Warnings.VisualCMissingWarning, warn_msg)
+        warn_msg = "Could not find requested MSVC compiler 'cl'."
+        if found_cl_envpath:
+            warn_msg += " A 'cl' was found on the scons ENV path which may be erroneous."
+        warn_msg += " %s"
+        debug(warn_msg, propose)
+        SCons.Warnings.warn(SCons.Warnings.VisualCMissingWarning, warn_msg % propose)
 
 def msvc_exists(env=None, version=None):
     vcs = get_installed_vcs(env)
diff --git a/test/MSVC/MSVC_USE_SETTINGS.py b/test/MSVC/MSVC_USE_SETTINGS.py
index 7c58c7b9a..fd6f85ceb 100644
--- a/test/MSVC/MSVC_USE_SETTINGS.py
+++ b/test/MSVC/MSVC_USE_SETTINGS.py
@@ -56,7 +56,7 @@ env = Environment(MSVC_USE_SETTINGS={})
 """ % locals())
 
 test.run(arguments="--warn=visual-c-missing .", status=0, stderr=None)
-test.must_contain_all(test.stderr(), "Could not find MSVC compiler 'cl'")
+test.must_contain_all(test.stderr(), "Could not find requested MSVC compiler 'cl'")
 
 test.write('SConstruct', """
 env = Environment(MSVC_USE_SETTINGS='dict or None')