From: José Matos <jamatos@lyx.org>
Date: Fri, 7 Jun 2019 14:27:25 +0000 (+0100)
Subject: Change python run time detection to privilege python 3 over python 2.
X-Git-Url: https://git.lyx.org/gitweb/?a=commitdiff_plain;h=7db6d73b3745dae0f558dc6b1c5c89f5b8154988;p=features.git

Change python run time detection to privilege python 3 over python 2.

This should work as before but now we also control the python version and ignore it if it is not in the supported range.
---

diff --git a/src/support/os.cpp b/src/support/os.cpp
index 8eea49370a..936e759b8b 100644
--- a/src/support/os.cpp
+++ b/src/support/os.cpp
@@ -11,9 +11,11 @@
 
 #include <config.h>
 
+#include "support/convert.h"
 #include "support/debug.h"
 #include "support/filetools.h"
 #include "support/qstring_helpers.h"
+#include "support/regex.h"
 
 #include <QDir>
 
@@ -40,18 +42,25 @@ namespace os {
 
 static string const python23(string const & binary, bool verbose = false)
 {
+	const string version_info = " -c 'from __future__ import print_function;import sys; print(sys.version_info[:2], end=\"\")'";
+	static regex const python_reg("\\((\\d*), (\\d*)\\)");
 	if (verbose)
 		lyxerr << "Examining " << binary << "\n";
 
 	// Check whether this is a python 2 or 3 binary.
-	cmd_ret const out = runCommand(binary + " -V 2>&1");
-	if (out.first < 0 ||
-	    (!prefixIs(out.second, "Python 2") &&
-	     !prefixIs(out.second, "Python 3")))
+	cmd_ret const out = runCommand(binary + version_info);
+
+	smatch sm;
+	if (out.first < 0 || !regex_match(out.second, sm, python_reg))
+		return string();
+
+	int major = convert<int>(sm.str(1));
+	int minor = convert<int>(sm.str(2));
+	if((major == 2 and minor < 7) or (major == 3 and minor < 4))
 		return string();
 
 	if (verbose)
-		lyxerr << "Found " << out.second << "\n";
+		lyxerr << "Found Python " << out.second << "\n";
 	return binary;
 }
 
@@ -64,26 +73,25 @@ int timeout_min()
 
 string const python(bool reset)
 {
-	// Check whether the first python in PATH is the right one.
-	static string command = python23("python -tt");
+	// Check whether python3 in PATH is the right one.
+	static string command = python23("python3");
 	// FIXME THREAD
 	if (reset) {
-		command = python23("python -tt");
+		command = python23("python3");
 	}
 
+	// python3 does not exists, let us try python3.x
 	if (command.empty()) {
 		// It was not, so check whether we can find it elsewhere in
 		// PATH, maybe with some suffix appended.
 		vector<string> const path = getEnvPath("PATH");
-		vector<string>::const_iterator it = path.begin();
-		vector<string>::const_iterator const end = path.end();
-		lyxerr << "Looking for python v2.x or 3.x ...\n";
-		for (; it != end; ++it) {
-			QString const dir = toqstr(*it);
+		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("python*"));
+			QStringList list = qdir.entryList(QStringList("python3*"));
 			for (int i = 0; i < list.size() && command.empty(); ++i) {
 				string const binary = addName(localdir,
 					list.at(i).toLocal8Bit().constData());
@@ -91,16 +99,42 @@ string const python(bool reset)
 			}
 		}
 
-		// Default to "python" if no usable binary was found.
-		if (command.empty()) {
-			lyxerr << "Warning: No python v2.x or 3.x binary found.\n";
-			command = "python";
+	}
+	// python 3 not found let us look for python 2
+	if (command.empty())
+		command = python23("python2");
+
+	// python2 does not exists, let us try python2.x
+	if (command.empty()) {
+		// It was not, so check whether we can find it elsewhere in
+		// PATH, maybe with some suffix appended.
+		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("python2*"));
+			for (int i = 0; i < list.size() && command.empty(); ++i) {
+				string const binary = addName(localdir,
+					list.at(i).toLocal8Bit().constData());
+				command = python23(binary, true);
+			}
 		}
 
-		// Add the -tt switch so that mixed tab/whitespace
-		// indentation is an error
-		command += " -tt";
 	}
+
+	// Default to "python" if no usable binary was found.
+	// If this happens all hope is lost that there is a sane system
+	if (command.empty()) {
+		lyxerr << "Warning: No python v2.x or 3.x binary found.\n";
+		command = "python";
+	}
+
+	// Add the -tt switch so that mixed tab/whitespace
+	// indentation is an error
+	command += " -tt";
 	return command;
 }