plpy_elog.c

Go to the documentation of this file.

/*
 * reporting Python exceptions as PostgreSQL errors
 *
 * src/pl/plpython/plpy_elog.c
 */

#include "postgres.h"

#include "lib/stringinfo.h"

#include "plpython.h"

#include "plpy_elog.h"

#include "plpy_main.h"
#include "plpy_procedure.h"


PyObject   *PLy_exc_error = NULL;
PyObject   *PLy_exc_fatal = NULL;
PyObject   *PLy_exc_spi_error = NULL;


static void PLy_traceback(char **xmsg, char **tbmsg, int *tb_depth);
static void PLy_get_spi_error_data(PyObject *exc, int *sqlerrcode, char **detail,
                       char **hint, char **query, int *position);
static char *get_source_line(const char *src, int lineno);


/*
 * Emit a PG error or notice, together with any available info about
 * the current Python error, previously set by PLy_exception_set().
 * This should be used to propagate Python errors into PG.  If fmt is
 * NULL, the Python error becomes the primary error message, otherwise
 * it becomes the detail.  If there is a Python traceback, it is put
 * in the context.
 */
void
PLy_elog(int elevel, const char *fmt,...)
{
    char       *xmsg;
    char       *tbmsg;
    int         tb_depth;
    StringInfoData emsg;
    PyObject   *exc,
               *val,
               *tb;
    const char *primary = NULL;
    int         sqlerrcode = 0;
    char       *detail = NULL;
    char       *hint = NULL;
    char       *query = NULL;
    int         position = 0;

    PyErr_Fetch(&exc, &val, &tb);
    if (exc != NULL)
    {
        if (PyErr_GivenExceptionMatches(val, PLy_exc_spi_error))
            PLy_get_spi_error_data(val, &sqlerrcode, &detail, &hint, &query, &position);
        else if (PyErr_GivenExceptionMatches(val, PLy_exc_fatal))
            elevel = FATAL;
    }
    PyErr_Restore(exc, val, tb);

    PLy_traceback(&xmsg, &tbmsg, &tb_depth);

    if (fmt)
    {
        initStringInfo(&emsg);
        for (;;)
        {
            va_list     ap;
            bool        success;

            va_start(ap, fmt);
            success = appendStringInfoVA(&emsg, dgettext(TEXTDOMAIN, fmt), ap);
            va_end(ap);
            if (success)
                break;
            enlargeStringInfo(&emsg, emsg.maxlen);
        }
        primary = emsg.data;

        /* Since we have a format string, we cannot have a SPI detail. */
        Assert(detail == NULL);

        /* If there's an exception message, it goes in the detail. */
        if (xmsg)
            detail = xmsg;
    }
    else
    {
        if (xmsg)
            primary = xmsg;
    }

    PG_TRY();
    {
        ereport(elevel,
                (errcode(sqlerrcode ? sqlerrcode : ERRCODE_INTERNAL_ERROR),
              errmsg_internal("%s", primary ? primary : "no exception data"),
                 (detail) ? errdetail_internal("%s", detail) : 0,
                 (tb_depth > 0 && tbmsg) ? errcontext("%s", tbmsg) : 0,
                 (hint) ? errhint("%s", hint) : 0,
                 (query) ? internalerrquery(query) : 0,
                 (position) ? internalerrposition(position) : 0));
    }
    PG_CATCH();
    {
        if (fmt)
            pfree(emsg.data);
        if (xmsg)
            pfree(xmsg);
        if (tbmsg)
            pfree(tbmsg);
        PG_RE_THROW();
    }
    PG_END_TRY();

    if (fmt)
        pfree(emsg.data);
    if (xmsg)
        pfree(xmsg);
    if (tbmsg)
        pfree(tbmsg);
}

/*
 * Extract a Python traceback from the current exception.
 *
 * The exception error message is returned in xmsg, the traceback in
 * tbmsg (both as palloc'd strings) and the traceback depth in
 * tb_depth.
 */
static void
PLy_traceback(char **xmsg, char **tbmsg, int *tb_depth)
{
    PyObject   *e,
               *v,
               *tb;
    PyObject   *e_type_o;
    PyObject   *e_module_o;
    char       *e_type_s = NULL;
    char       *e_module_s = NULL;
    PyObject   *vob = NULL;
    char       *vstr;
    StringInfoData xstr;
    StringInfoData tbstr;

    /*
     * get the current exception
     */
    PyErr_Fetch(&e, &v, &tb);

    /*
     * oops, no exception, return
     */
    if (e == NULL)
    {
        *xmsg = NULL;
        *tbmsg = NULL;
        *tb_depth = 0;

        return;
    }

    PyErr_NormalizeException(&e, &v, &tb);

    /*
     * Format the exception and its value and put it in xmsg.
     */

    e_type_o = PyObject_GetAttrString(e, "__name__");
    e_module_o = PyObject_GetAttrString(e, "__module__");
    if (e_type_o)
        e_type_s = PyString_AsString(e_type_o);
    if (e_type_s)
        e_module_s = PyString_AsString(e_module_o);

    if (v && ((vob = PyObject_Str(v)) != NULL))
        vstr = PyString_AsString(vob);
    else
        vstr = "unknown";

    initStringInfo(&xstr);
    if (!e_type_s || !e_module_s)
    {
        if (PyString_Check(e))
            /* deprecated string exceptions */
            appendStringInfoString(&xstr, PyString_AsString(e));
        else
            /* shouldn't happen */
            appendStringInfoString(&xstr, "unrecognized exception");
    }
    /* mimics behavior of traceback.format_exception_only */
    else if (strcmp(e_module_s, "builtins") == 0
             || strcmp(e_module_s, "__main__") == 0
             || strcmp(e_module_s, "exceptions") == 0)
        appendStringInfo(&xstr, "%s", e_type_s);
    else
        appendStringInfo(&xstr, "%s.%s", e_module_s, e_type_s);
    appendStringInfo(&xstr, ": %s", vstr);

    *xmsg = xstr.data;

    /*
     * Now format the traceback and put it in tbmsg.
     */

    *tb_depth = 0;
    initStringInfo(&tbstr);
    /* Mimick Python traceback reporting as close as possible. */
    appendStringInfoString(&tbstr, "Traceback (most recent call last):");
    while (tb != NULL && tb != Py_None)
    {
        PyObject   *volatile tb_prev = NULL;
        PyObject   *volatile frame = NULL;
        PyObject   *volatile code = NULL;
        PyObject   *volatile name = NULL;
        PyObject   *volatile lineno = NULL;
        PyObject   *volatile filename = NULL;

        PG_TRY();
        {
            lineno = PyObject_GetAttrString(tb, "tb_lineno");
            if (lineno == NULL)
                elog(ERROR, "could not get line number from Python traceback");

            frame = PyObject_GetAttrString(tb, "tb_frame");
            if (frame == NULL)
                elog(ERROR, "could not get frame from Python traceback");

            code = PyObject_GetAttrString(frame, "f_code");
            if (code == NULL)
                elog(ERROR, "could not get code object from Python frame");

            name = PyObject_GetAttrString(code, "co_name");
            if (name == NULL)
                elog(ERROR, "could not get function name from Python code object");

            filename = PyObject_GetAttrString(code, "co_filename");
            if (filename == NULL)
                elog(ERROR, "could not get file name from Python code object");
        }
        PG_CATCH();
        {
            Py_XDECREF(frame);
            Py_XDECREF(code);
            Py_XDECREF(name);
            Py_XDECREF(lineno);
            Py_XDECREF(filename);
            PG_RE_THROW();
        }
        PG_END_TRY();

        /* The first frame always points at <module>, skip it. */
        if (*tb_depth > 0)
        {
            PLyExecutionContext *exec_ctx = PLy_current_execution_context();
            char       *proname;
            char       *fname;
            char       *line;
            char       *plain_filename;
            long        plain_lineno;

            /*
             * The second frame points at the internal function, but to mimick
             * Python error reporting we want to say <module>.
             */
            if (*tb_depth == 1)
                fname = "<module>";
            else
                fname = PyString_AsString(name);

            proname = PLy_procedure_name(exec_ctx->curr_proc);
            plain_filename = PyString_AsString(filename);
            plain_lineno = PyInt_AsLong(lineno);

            if (proname == NULL)
                appendStringInfo(
                &tbstr, "\n  PL/Python anonymous code block, line %ld, in %s",
                                 plain_lineno - 1, fname);
            else
                appendStringInfo(
                    &tbstr, "\n  PL/Python function \"%s\", line %ld, in %s",
                                 proname, plain_lineno - 1, fname);

            /*
             * function code object was compiled with "<string>" as the
             * filename
             */
            if (exec_ctx->curr_proc && plain_filename != NULL &&
                strcmp(plain_filename, "<string>") == 0)
            {
                /*
                 * If we know the current procedure, append the exact line
                 * from the source, again mimicking Python's traceback.py
                 * module behavior.  We could store the already line-split
                 * source to avoid splitting it every time, but producing a
                 * traceback is not the most important scenario to optimize
                 * for.  But we do not go as far as traceback.py in reading
                 * the source of imported modules.
                 */
                line = get_source_line(exec_ctx->curr_proc->src, plain_lineno);
                if (line)
                {
                    appendStringInfo(&tbstr, "\n    %s", line);
                    pfree(line);
                }
            }
        }

        Py_DECREF(frame);
        Py_DECREF(code);
        Py_DECREF(name);
        Py_DECREF(lineno);
        Py_DECREF(filename);

        /* Release the current frame and go to the next one. */
        tb_prev = tb;
        tb = PyObject_GetAttrString(tb, "tb_next");
        Assert(tb_prev != Py_None);
        Py_DECREF(tb_prev);
        if (tb == NULL)
            elog(ERROR, "could not traverse Python traceback");
        (*tb_depth)++;
    }

    /* Return the traceback. */
    *tbmsg = tbstr.data;

    Py_XDECREF(e_type_o);
    Py_XDECREF(e_module_o);
    Py_XDECREF(vob);
    Py_XDECREF(v);
    Py_DECREF(e);
}

/*
 * Extract error code from SPIError's sqlstate attribute.
 */
static void
PLy_get_spi_sqlerrcode(PyObject *exc, int *sqlerrcode)
{
    PyObject    *sqlstate;
    char        *buffer;

    sqlstate = PyObject_GetAttrString(exc, "sqlstate");
    if (sqlstate == NULL)
        return;

    buffer = PyString_AsString(sqlstate);
    if (strlen(buffer) == 5 &&
        strspn(buffer, "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ") == 5)
    {
        *sqlerrcode = MAKE_SQLSTATE(buffer[0], buffer[1], buffer[2],
                                    buffer[3], buffer[4]);
    }

    Py_DECREF(sqlstate);
}


/*
 * Extract the error data from a SPIError
 */
static void
PLy_get_spi_error_data(PyObject *exc, int *sqlerrcode, char **detail, char **hint, char **query, int *position)
{
    PyObject   *spidata = NULL;

    spidata = PyObject_GetAttrString(exc, "spidata");

    if (spidata != NULL)
    {
        PyArg_ParseTuple(spidata, "izzzi", sqlerrcode, detail, hint, query, position);
    }
    else
    {
        /*
         * If there's no spidata, at least set the sqlerrcode. This can happen
         * if someone explicitly raises a SPI exception from Python code.
         */
        PLy_get_spi_sqlerrcode(exc, sqlerrcode);
    }

    PyErr_Clear();
    /* no elog here, we simply won't report the errhint, errposition etc */
    Py_XDECREF(spidata);
}

/*
 * Get the given source line as a palloc'd string
 */
static char *
get_source_line(const char *src, int lineno)
{
    const char *s = NULL;
    const char *next = src;
    int         current = 0;

    /* sanity check */
    if (lineno <= 0)
        return NULL;

    while (current < lineno)
    {
        s = next;
        next = strchr(s + 1, '\n');
        current++;
        if (next == NULL)
            break;
    }

    if (current != lineno)
        return NULL;

    while (*s && isspace((unsigned char) *s))
        s++;

    if (next == NULL)
        return pstrdup(s);

    /*
     * Sanity check, next < s if the line was all-whitespace, which should
     * never happen if Python reported a frame created on that line, but check
     * anyway.
     */
    if (next < s)
        return NULL;

    return pnstrdup(s, next - s);
}


/* call PyErr_SetString with a vprint interface and translation support */
void
PLy_exception_set(PyObject *exc, const char *fmt,...)
{
    char        buf[1024];
    va_list     ap;

    va_start(ap, fmt);
    vsnprintf(buf, sizeof(buf), dgettext(TEXTDOMAIN, fmt), ap);
    va_end(ap);

    PyErr_SetString(exc, buf);
}

/* same, with pluralized message */
void
PLy_exception_set_plural(PyObject *exc,
                         const char *fmt_singular, const char *fmt_plural,
                         unsigned long n,...)
{
    char        buf[1024];
    va_list     ap;

    va_start(ap, n);
    vsnprintf(buf, sizeof(buf),
              dngettext(TEXTDOMAIN, fmt_singular, fmt_plural, n),
              ap);
    va_end(ap);

    PyErr_SetString(exc, buf);
}