Divide the python detection in three functions, with a clear delegation of responsibi...

python23_call: determines if the binary given is appropriate and adds the necessary calling options

find_python_binary: get a list of candidates and choose the right one using python23_call

python: returns the name of the python interpreter that can be found on PATH, using find_python_binary

diff --git a/src/support/os.cpp b/src/support/os.cpp
index 58d9d433a151dbff3a675c747babbb08e9ea1c40..9840ad3f4574b8673f18bdb60541d5078b4393a6 100644 (file)
--- a/src/support/os.cpp
+++ b/src/support/os.cpp
@@ -46,13 +46,16 @@ int timeout_min()
 }
 
 
-static string const python23(string const & binary, bool verbose = false)
+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=\"\")'";
        static regex const python_reg("\\((\\d*), (\\d*)\\)");
+       // Default to "python" if no binary is given.
+       if (binary.empty())
+               return "python -tt";
+
        if (verbose)
                lyxerr << "Examining " << binary << "\n";
-
        // Check whether this is a python 2 or 3 binary.
        cmd_ret const out = runCommand(binary + version_info);
 
@@ -67,11 +70,13 @@ static string const python23(string const & binary, bool verbose = false)
 
        if (verbose)
                lyxerr << "Found Python " << out.second << "\n";
-       return binary;
+       // Add the -tt switch so that mixed tab/whitespace
+       // indentation is an error
+       return binary + " -tt";
 }
 
 
-string const python(bool reset)
+static string const find_python_binary()
 {
        // This function takes inspiration from PEP 394 and PEP 397
        // PEP 394 -- The "python" Command on Unix-Like Systems
@@ -80,67 +85,67 @@ string const python(bool reset)
        // https://www.python.org/dev/peps/pep-0397/
 
        // Check whether python3 in PATH is the right one.
-       static string command = python23("python3");
-       // FIXME THREAD
-       if (reset) {
-               command = python23("python3");
-       }
+       string command = python23_call("python3");
+       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
-       if (command.empty()) {
-               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 (int i = 0; i < list.size() && command.empty(); ++i) {
-                               string const binary = addName(localdir,
-                                       list.at(i).toLocal8Bit().constData());
-                               command = python23(binary, true);
-                       }
+       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 bin: list) {
+                       string const binary = addName(localdir,
+                               bin.toLocal8Bit().constData());
+                       command = python23_call(binary, true);
+                       if (!command.empty())
+                               return command;
                }
-
        }
+
        // python 3 was not found let us look for python 2
-       if (command.empty())
-               command = python23("python2");
+       command = python23_call("python2");
+       if (!command.empty())
+               return command;
 
        // python2 does not exists, let us try to find python2.x in PATH
        // the search is probably broader than required
        // but we are trying hard to find a valid python binary
-       if (command.empty()) {
-               vector<string> const path = getEnvPath("PATH");
-               lyxerr << "Looking for python 2.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);
-                       }
+       lyxerr << "Looking for python 2.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 (auto bin: list) {
+                       string const binary = addName(localdir,
+                               bin.toLocal8Bit().constData());
+                       command = python23_call(binary, true);
+                       if (!command.empty())
+                               return command;
                }
-
        }
 
-       // Default to "python" if no usable binary was found.
        // If this happens all hope is lost that this is a sane system
-       if (command.empty()) {
-               lyxerr << "Warning: No python v2.x or 3.x binary found.\n";
-               command = "python";
-       }
+       lyxerr << "Warning: No python v2.x or 3.x binary found.\n";
+       return python23_call("");
+}
 
-       // Add the -tt switch so that mixed tab/whitespace
-       // indentation is an error
-       command += " -tt";
+
+string const python(bool reset)
+{
+       static string command = find_python_binary();
+       // FIXME THREAD
+       if (reset) {
+               command = find_python_binary();
+       }
        return command;
 }