postgresql/src/pl/plpython/plpy_elog.c

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

#include "postgres.h"

#include "lib/stringinfo.h"
#include "plpy_elog.h"
#include "plpy_main.h"
#include "plpy_procedure.h"
#include "plpython.h"

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


static void PLy_traceback(PyObject *e, PyObject *v, PyObject *tb,
						  char *volatile *xmsg, char *volatile *tbmsg,
						  int *tb_depth);
static void PLy_get_spi_error_data(PyObject *exc, int *sqlerrcode, char **detail,
								   char **hint, char **query, int *position,
								   char **schema_name, char **table_name, char **column_name,
								   char **datatype_name, char **constraint_name);
static void PLy_get_error_data(PyObject *exc, int *sqlerrcode, char **detail,
							   char **hint, char **schema_name, char **table_name, char **column_name,
							   char **datatype_name, char **constraint_name);
static char *get_source_line(const char *src, int lineno);

static void get_string_attr(PyObject *obj, char *attrname, char **str);
static bool set_string_attr(PyObject *obj, char *attrname, char *str);

/*
 * 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_impl(int elevel, const char *fmt,...)
{
	int			save_errno = errno;
	char	   *volatile xmsg = NULL;
	char	   *volatile tbmsg = NULL;
	int			tb_depth;
	StringInfoData emsg;
	PyObject   *exc,
			   *val,
			   *tb;

	/* If we'll need emsg, must initialize it before entering PG_TRY */
	if (fmt)
		initStringInfo(&emsg);

	PyErr_Fetch(&exc, &val, &tb);

	/* Use a PG_TRY block to ensure we release the PyObjects just acquired */
	PG_TRY();
	{
		const char *primary = NULL;
		int			sqlerrcode = 0;
		char	   *detail = NULL;
		char	   *hint = NULL;
		char	   *query = NULL;
		int			position = 0;
		char	   *schema_name = NULL;
		char	   *table_name = NULL;
		char	   *column_name = NULL;
		char	   *datatype_name = NULL;
		char	   *constraint_name = NULL;

		if (exc != NULL)
		{
			PyErr_NormalizeException(&exc, &val, &tb);

			if (PyErr_GivenExceptionMatches(val, PLy_exc_spi_error))
				PLy_get_spi_error_data(val, &sqlerrcode,
									   &detail, &hint, &query, &position,
									   &schema_name, &table_name, &column_name,
									   &datatype_name, &constraint_name);
			else if (PyErr_GivenExceptionMatches(val, PLy_exc_error))
				PLy_get_error_data(val, &sqlerrcode, &detail, &hint,
								   &schema_name, &table_name, &column_name,
								   &datatype_name, &constraint_name);
			else if (PyErr_GivenExceptionMatches(val, PLy_exc_fatal))
				elevel = FATAL;
		}

		PLy_traceback(exc, val, tb,
					  &xmsg, &tbmsg, &tb_depth);

		if (fmt)
		{
			for (;;)
			{
				va_list		ap;
				int			needed;

				errno = save_errno;
				va_start(ap, fmt);
				needed = appendStringInfoVA(&emsg, dgettext(TEXTDOMAIN, fmt), ap);
				va_end(ap);
				if (needed == 0)
					break;
				enlargeStringInfo(&emsg, needed);
			}
			primary = emsg.data;

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

		ereport(elevel,
				(errcode(sqlerrcode ? sqlerrcode : ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
				 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,
				 (schema_name) ? err_generic_string(PG_DIAG_SCHEMA_NAME,
													schema_name) : 0,
				 (table_name) ? err_generic_string(PG_DIAG_TABLE_NAME,
												   table_name) : 0,
				 (column_name) ? err_generic_string(PG_DIAG_COLUMN_NAME,
													column_name) : 0,
				 (datatype_name) ? err_generic_string(PG_DIAG_DATATYPE_NAME,
													  datatype_name) : 0,
				 (constraint_name) ? err_generic_string(PG_DIAG_CONSTRAINT_NAME,
														constraint_name) : 0));
	}
	PG_FINALLY();
	{
		Py_XDECREF(exc);
		Py_XDECREF(val);
		Py_XDECREF(tb);
		/* For neatness' sake, also release our string buffers */
		if (fmt)
			pfree(emsg.data);
		if (xmsg)
			pfree(xmsg);
		if (tbmsg)
			pfree(tbmsg);
	}
	PG_END_TRY();
}

/*
 * Extract a Python traceback from the given exception data.
 *
 * 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(PyObject *e, PyObject *v, PyObject *tb,
			  char *volatile *xmsg, char *volatile *tbmsg, int *tb_depth)
{
	PyObject   *volatile e_type_o = NULL;
	PyObject   *volatile e_module_o = NULL;
	PyObject   *volatile vob = NULL;
	StringInfoData tbstr;

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

		return;
	}

	/*
	 * Format the exception and its value and put it in xmsg.
	 */
	PG_TRY();
	{
		char	   *e_type_s = NULL;
		char	   *e_module_s = NULL;
		const char *vstr;
		StringInfoData xstr;

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

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

		initStringInfo(&xstr);
		if (!e_type_s || !e_module_s)
		{
			/* 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)
			appendStringInfoString(&xstr, e_type_s);
		else
			appendStringInfo(&xstr, "%s.%s", e_module_s, e_type_s);
		appendStringInfo(&xstr, ": %s", vstr);

		*xmsg = xstr.data;
	}
	PG_FINALLY();
	{
		Py_XDECREF(e_type_o);
		Py_XDECREF(e_module_o);
		Py_XDECREF(vob);
	}
	PG_END_TRY();

	/*
	 * Now format the traceback and put it in tbmsg.
	 */
	*tb_depth = 0;
	initStringInfo(&tbstr);
	/* Mimic Python traceback reporting as close as possible. */
	appendStringInfoString(&tbstr, "Traceback (most recent call last):");
	while (tb != NULL && tb != Py_None)
	{
		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");

			/* 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
				 * mimic Python error reporting we want to say <module>.
				 */
				if (*tb_depth == 1)
					fname = "<module>";
				else
					fname = PLyUnicode_AsString(name);

				proname = PLy_procedure_name(exec_ctx->curr_proc);
				plain_filename = PLyUnicode_AsString(filename);
				plain_lineno = PyLong_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);
					}
				}
			}
		}
		PG_FINALLY();
		{
			Py_XDECREF(frame);
			Py_XDECREF(code);
			Py_XDECREF(name);
			Py_XDECREF(lineno);
			Py_XDECREF(filename);
		}
		PG_END_TRY();

		/* Advance to the next frame. */
		tb = PyObject_GetAttrString(tb, "tb_next");
		if (tb == NULL)
			elog(ERROR, "could not traverse Python traceback");

		/*
		 * Release the refcount that PyObject_GetAttrString acquired on the
		 * next frame object.  We don't need it, because our caller has a
		 * refcount on the first frame object and the frame objects each have
		 * a refcount on the next one.  If we tried to hold this refcount
		 * longer, it would greatly complicate cleanup in the event of a
		 * failure in the above PG_TRY block.
		 */
		Py_DECREF(tb);

		(*tb_depth)++;
	}

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

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

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

	buffer = PLyUnicode_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
 *
 * Note: the returned string values are pointers into the given PyObject.
 * They must not be free()'d, and are not guaranteed to be valid once
 * we stop holding a reference on the PyObject.
 */
static void
PLy_get_spi_error_data(PyObject *exc, int *sqlerrcode, char **detail,
					   char **hint, char **query, int *position,
					   char **schema_name, char **table_name,
					   char **column_name,
					   char **datatype_name, char **constraint_name)
{
	PyObject   *spidata;

	spidata = PyObject_GetAttrString(exc, "spidata");

	if (spidata != NULL)
	{
		PyArg_ParseTuple(spidata, "izzzizzzzz",
						 sqlerrcode, detail, hint, query, position,
						 schema_name, table_name, column_name,
						 datatype_name, constraint_name);
	}
	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_sqlerrcode(exc, sqlerrcode);
	}

	Py_XDECREF(spidata);
}

/*
 * Extract the error data from an Error.
 *
 * Note: position and query attributes are never set for Error so, unlike
 * PLy_get_spi_error_data, this function doesn't return them.
 *
 * Note: the returned string values are palloc'd in the current context.
 * While our caller could pfree them later, there's no real need to do so,
 * and it would be complicated to handle both this convention and that of
 * PLy_get_spi_error_data.
 */
static void
PLy_get_error_data(PyObject *exc, int *sqlerrcode, char **detail, char **hint,
				   char **schema_name, char **table_name, char **column_name,
				   char **datatype_name, char **constraint_name)
{
	PLy_get_sqlerrcode(exc, sqlerrcode);
	get_string_attr(exc, "detail", detail);
	get_string_attr(exc, "hint", hint);
	get_string_attr(exc, "schema_name", schema_name);
	get_string_attr(exc, "table_name", table_name);
	get_string_attr(exc, "column_name", column_name);
	get_string_attr(exc, "datatype_name", datatype_name);
	get_string_attr(exc, "constraint_name", constraint_name);
}

/*
 * 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);
}

/* set attributes of the given exception to details from ErrorData */
void
PLy_exception_set_with_details(PyObject *excclass, ErrorData *edata)
{
	PyObject   *args = NULL;
	PyObject   *error = NULL;

	args = Py_BuildValue("(s)", edata->message);
	if (!args)
		goto failure;

	/* create a new exception with the error message as the parameter */
	error = PyObject_CallObject(excclass, args);
	if (!error)
		goto failure;

	if (!set_string_attr(error, "sqlstate",
						 unpack_sql_state(edata->sqlerrcode)))
		goto failure;

	if (!set_string_attr(error, "detail", edata->detail))
		goto failure;

	if (!set_string_attr(error, "hint", edata->hint))
		goto failure;

	if (!set_string_attr(error, "query", edata->internalquery))
		goto failure;

	if (!set_string_attr(error, "schema_name", edata->schema_name))
		goto failure;

	if (!set_string_attr(error, "table_name", edata->table_name))
		goto failure;

	if (!set_string_attr(error, "column_name", edata->column_name))
		goto failure;

	if (!set_string_attr(error, "datatype_name", edata->datatype_name))
		goto failure;

	if (!set_string_attr(error, "constraint_name", edata->constraint_name))
		goto failure;

	PyErr_SetObject(excclass, error);

	Py_DECREF(args);
	Py_DECREF(error);

	return;

failure:
	Py_XDECREF(args);
	Py_XDECREF(error);

	elog(ERROR, "could not convert error to Python exception");
}

/* get string value of an object attribute */
static void
get_string_attr(PyObject *obj, char *attrname, char **str)
{
	PyObject   *val;

	val = PyObject_GetAttrString(obj, attrname);
	if (val != NULL && val != Py_None)
	{
		*str = pstrdup(PLyUnicode_AsString(val));
	}
	Py_XDECREF(val);
}

/* set an object attribute to a string value, returns true when the set was
 * successful
 */
static bool
set_string_attr(PyObject *obj, char *attrname, char *str)
{
	int			result;
	PyObject   *val;

	if (str != NULL)
	{
		val = PLyUnicode_FromString(str);
		if (!val)
			return false;
	}
	else
	{
		val = Py_None;
		Py_INCREF(Py_None);
	}

	result = PyObject_SetAttrString(obj, attrname, val);
	Py_DECREF(val);

	return result != -1;
}