eval.h

/*
    pybind11/exec.h: Support for evaluating Python expressions and statements
    from strings and files

    Copyright (c) 2016 Klemens Morgenstern <klemens.morgenstern@ed-chemnitz.de> and
                       Wenzel Jakob <wenzel.jakob@epfl.ch>

    All rights reserved. Use of this source code is governed by a
    BSD-style license that can be found in the LICENSE file.
*/

#pragma once

#include "pybind11.h"

PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
PYBIND11_NAMESPACE_BEGIN(detail)

inline void ensure_builtins_in_globals(object &global) {
    #if PY_VERSION_HEX < 0x03080000
        // Running exec and eval on Python 2 and 3 adds `builtins` module under
        // `__builtins__` key to globals if not yet present.
        // Python 3.8 made PyRun_String behave similarly. Let's also do that for
        // older versions, for consistency.
        if (!global.contains("__builtins__"))
            global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
    #else
        (void) global;
    #endif
}

PYBIND11_NAMESPACE_END(detail)

enum eval_mode {
    /// Evaluate a string containing an isolated expression
    eval_expr,

    /// Evaluate a string containing a single statement. Returns \c none
    eval_single_statement,

    /// Evaluate a string containing a sequence of statement. Returns \c none
    eval_statements
};

template <eval_mode mode = eval_expr>
object eval(str expr, object global = globals(), object local = object()) {
    if (!local)
        local = global;

    detail::ensure_builtins_in_globals(global);

    /* PyRun_String does not accept a PyObject / encoding specifier,
       this seems to be the only alternative */
    std::string buffer = "# -*- coding: utf-8 -*-\n" + (std::string) expr;

    int start;
    switch (mode) {
        case eval_expr:             start = Py_eval_input;   break;
        case eval_single_statement: start = Py_single_input; break;
        case eval_statements:       start = Py_file_input;   break;
        default: pybind11_fail("invalid evaluation mode");
    }

    PyObject *result = PyRun_String(buffer.c_str(), start, global.ptr(), local.ptr());
    if (!result)
        throw error_already_set();
    return reinterpret_steal<object>(result);
}

template <eval_mode mode = eval_expr, size_t N>
object eval(const char (&s)[N], object global = globals(), object local = object()) {
    /* Support raw string literals by removing common leading whitespace */
    auto expr = (s[0] == '\n') ? str(module_::import("textwrap").attr("dedent")(s))
                               : str(s);
    return eval<mode>(expr, global, local);
}

inline void exec(str expr, object global = globals(), object local = object()) {
    eval<eval_statements>(expr, global, local);
}

template <size_t N>
void exec(const char (&s)[N], object global = globals(), object local = object()) {
    eval<eval_statements>(s, global, local);
}

#if defined(PYPY_VERSION) && PY_VERSION_HEX >= 0x03000000
template <eval_mode mode = eval_statements>
object eval_file(str, object, object) {
    pybind11_fail("eval_file not supported in PyPy3. Use eval");
}
template <eval_mode mode = eval_statements>
object eval_file(str, object) {
    pybind11_fail("eval_file not supported in PyPy3. Use eval");
}
template <eval_mode mode = eval_statements>
object eval_file(str) {
    pybind11_fail("eval_file not supported in PyPy3. Use eval");
}
#else
template <eval_mode mode = eval_statements>
object eval_file(str fname, object global = globals(), object local = object()) {
    if (!local)
        local = global;

    detail::ensure_builtins_in_globals(global);

    int start;
    switch (mode) {
        case eval_expr:             start = Py_eval_input;   break;
        case eval_single_statement: start = Py_single_input; break;
        case eval_statements:       start = Py_file_input;   break;
        default: pybind11_fail("invalid evaluation mode");
    }

    int closeFile = 1;
    std::string fname_str = (std::string) fname;
#if PY_VERSION_HEX >= 0x03040000
    FILE *f = _Py_fopen_obj(fname.ptr(), "r");
#elif PY_VERSION_HEX >= 0x03000000
    FILE *f = _Py_fopen(fname.ptr(), "r");
#else
    /* No unicode support in open() :( */
    auto fobj = reinterpret_steal<object>(PyFile_FromString(
        const_cast<char *>(fname_str.c_str()),
        const_cast<char*>("r")));
    FILE *f = nullptr;
    if (fobj)
        f = PyFile_AsFile(fobj.ptr());
    closeFile = 0;
#endif
    if (!f) {
        PyErr_Clear();
        pybind11_fail("File \"" + fname_str + "\" could not be opened!");
    }

#if PY_VERSION_HEX < 0x03000000 && defined(PYPY_VERSION)
    PyObject *result = PyRun_File(f, fname_str.c_str(), start, global.ptr(),
                                  local.ptr());
    (void) closeFile;
#else
    PyObject *result = PyRun_FileEx(f, fname_str.c_str(), start, global.ptr(),
                                    local.ptr(), closeFile);
#endif

    if (!result)
        throw error_already_set();
    return reinterpret_steal<object>(result);
}
#endif

PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)