[LyX/master] Fix bug #11712.

[Richard Kimberly Heck]

commit fdf81a9bab2f4f50a3eaf22cc0e09ac454f470ed
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Wed Feb 12 09:25:13 2020 -0500

    Fix bug #11712.
    
    Fixes some escaping issues on Windows especially
    
    Patch from Eugene.
---
 src/support/filetools.cpp |    4 ++--
 src/support/os.cpp        |   40 +++++++++++-----------------------------
 2 files changed, 13 insertions(+), 31 deletions(-)

diff --git a/src/support/filetools.cpp b/src/support/filetools.cpp
index e811995..bca242d 100644
--- a/src/support/filetools.cpp
+++ b/src/support/filetools.cpp
@@ -635,7 +635,7 @@ string const addName(string const & path, string const & fname)
 
 	if (path != "." && path != "./" && !path.empty()) {
 		buf = os::internal_path(path);
-		if (!suffixIs(path, '/'))
+		if (!suffixIs(buf, '/'))
 			buf += '/';
 	}
 
@@ -1039,7 +1039,7 @@ cmd_ret const runCommand(string const & cmd)
 		command = rtrim(command, "2>&1");
 		err2out = true;
 	}
-	string const cmdarg = "/d /c " + command;
+	string const cmdarg = "/d /c \"" + command+"\"";
 	string const comspec = getEnv("COMSPEC");
 
 	security.nLength = sizeof(SECURITY_ATTRIBUTES);
diff --git a/src/support/os.cpp b/src/support/os.cpp
index 10430bf..b1e4e09 100644
--- a/src/support/os.cpp
+++ b/src/support/os.cpp
@@ -48,7 +48,7 @@ int timeout_min()
 
 static string const python23_call(string const & binary, bool verbose = false)
 {
-	const string version_info = " -c 'from __future__ import print_function;import sys; print(sys.version_info[:2], end=\"\")'";
+	const string version_info = " -c \"from __future__ import print_function;import sys; print(sys.version_info[:2], end=\\\"\\\")\"";
 	// Default to "python" if no binary is given.
 	if (binary.empty())
 		return "python -tt";
@@ -89,49 +89,31 @@ static string const find_python_binary()
 	// PEP 397 -- Python launcher for Windows
 	// https://www.python.org/dev/peps/pep-0397/
 
-	// Check whether python3 in PATH is the right one.
-	string command = python23_call("python3");
+	// Check through python launcher whether python3 is
+	// installed on computer.
+	string command = python23_call("py -3");
 	if (!command.empty())
 		return command;
 
-	// python3 does not exists, let us try to find python3.x in PATH
-	// the search is probably broader than required
-	// but we are trying hard to find a valid python binary
-	vector<string> const path = getEnvPath("PATH");
-	lyxerr << "Looking for python 3.x ...\n";
-	for (auto bin : path) {
-		QString const dir = toqstr(bin);
-		string const localdir = dir.toLocal8Bit().constData();
-		QDir qdir(dir);
-		qdir.setFilter(QDir::Files | QDir::Executable);
-		QStringList list = qdir.entryList(QStringList("python3*"));
-		for (auto bin2 : list) {
-			string const binary = addName(localdir,
-				bin2.toLocal8Bit().constData());
-			command = python23_call(binary, true);
-			if (!command.empty())
-				return command;
-		}
-	}
-
 	// python 3 was not found let us look for python 2
-	command = python23_call("python2");
+	command = python23_call("py -2");
 	if (!command.empty())
 		return command;
 
-	// python2 does not exists, let us try to find python2.x in PATH
+	// python3 does not exists, let us try to find python3.x in PATH
 	// the search is probably broader than required
 	// but we are trying hard to find a valid python binary
-	lyxerr << "Looking for python 2.x ...\n";
+	vector<string> const path = getEnvPath("PATH");
+	lyxerr << "Looking for python in PATH ...\n";
 	for (auto bin : path) {
 		QString const dir = toqstr(bin);
 		string const localdir = dir.toLocal8Bit().constData();
 		QDir qdir(dir);
 		qdir.setFilter(QDir::Files | QDir::Executable);
-		QStringList list = qdir.entryList(QStringList("python2*"));
+		QStringList list = qdir.entryList(QStringList("python*"));
 		for (auto bin2 : list) {
-			string const binary = addName(localdir,
-				bin2.toLocal8Bit().constData());
+			string const binary = "\"" + addName(localdir,
+				bin2.toLocal8Bit().constData()) + "\"";
 			command = python23_call(binary, true);
 			if (!command.empty())
 				return command;