Add traceback information to PL/Python errors

This mimics the traceback information the Python interpreter prints
with exceptions.

Jan Urbański

Author: petere

src/pl/plpython/expected/plpython_do.out

@@ -3,4 +3,7 @@ NOTICE:  This is plpythonu.
 CONTEXT:  PL/Python anonymous code block
 DO $$ nonsense $$ LANGUAGE plpythonu;
 ERROR:  NameError: global name 'nonsense' is not defined
-CONTEXT:  PL/Python anonymous code block
+CONTEXT:  Traceback (most recent call last):
+  PL/Python anonymous code block, line 1, in <module>
+    nonsense 
+PL/Python anonymous code block

src/pl/plpython/expected/plpython_error.out

@@ -36,7 +36,10 @@ ERROR:  spiexceptions.SyntaxError: syntax error at or near "syntax"
 LINE 1: syntax error
         ^
 QUERY:  syntax error
-CONTEXT:  PL/Python function "sql_syntax_error"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "sql_syntax_error", line 1, in <module>
+    plpy.execute("syntax error")
+PL/Python function "sql_syntax_error"
 /* check the handling of uncaught python exceptions
  */
 CREATE FUNCTION exception_index_invalid(text) RETURNS text
@@ -45,7 +48,10 @@ CREATE FUNCTION exception_index_invalid(text) RETURNS text
 	LANGUAGE plpythonu;
 SELECT exception_index_invalid('test');
 ERROR:  IndexError: list index out of range
-CONTEXT:  PL/Python function "exception_index_invalid"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "exception_index_invalid", line 1, in <module>
+    return args[1]
+PL/Python function "exception_index_invalid"
 /* check handling of nested exceptions
  */
 CREATE FUNCTION exception_index_invalid_nested() RETURNS text
@@ -59,7 +65,10 @@ LINE 1: SELECT test5('foo')
                ^
 HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
 QUERY:  SELECT test5('foo')
-CONTEXT:  PL/Python function "exception_index_invalid_nested"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "exception_index_invalid_nested", line 1, in <module>
+    rv = plpy.execute("SELECT test5('foo')")
+PL/Python function "exception_index_invalid_nested"
 /* a typo
  */
 CREATE FUNCTION invalid_type_uncaught(a text) RETURNS text
@@ -75,7 +84,10 @@ return None
 	LANGUAGE plpythonu;
 SELECT invalid_type_uncaught('rick');
 ERROR:  spiexceptions.UndefinedObject: type "test" does not exist
-CONTEXT:  PL/Python function "invalid_type_uncaught"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "invalid_type_uncaught", line 3, in <module>
+    SD["plan"] = plpy.prepare(q, [ "test" ])
+PL/Python function "invalid_type_uncaught"
 /* for what it's worth catch the exception generated by
  * the typo, and return None
  */
@@ -121,7 +133,10 @@ return None
 	LANGUAGE plpythonu;
 SELECT invalid_type_reraised('rick');
 ERROR:  plpy.Error: type "test" does not exist
-CONTEXT:  PL/Python function "invalid_type_reraised"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "invalid_type_reraised", line 6, in <module>
+    plpy.error(str(ex))
+PL/Python function "invalid_type_reraised"
 /* no typo no messing about
  */
 CREATE FUNCTION valid_type(a text) RETURNS text
@@ -140,6 +155,164 @@ SELECT valid_type('rick');
 
 (1 row)
 
+/* error in nested functions to get a traceback
+*/
+CREATE FUNCTION nested_error() RETURNS text
+	AS
+'def fun1():
+	plpy.error("boom")
+
+def fun2():
+	fun1()
+
+def fun3():
+	fun2()
+
+fun3()
+return "not reached"
+'
+	LANGUAGE plpythonu;
+SELECT nested_error();
+ERROR:  plpy.Error: boom
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "nested_error", line 10, in <module>
+    fun3()
+  PL/Python function "nested_error", line 8, in fun3
+    fun2()
+  PL/Python function "nested_error", line 5, in fun2
+    fun1()
+  PL/Python function "nested_error", line 2, in fun1
+    plpy.error("boom")
+PL/Python function "nested_error"
+/* raising plpy.Error is just like calling plpy.error
+*/
+CREATE FUNCTION nested_error_raise() RETURNS text
+	AS
+'def fun1():
+	raise plpy.Error("boom")
+
+def fun2():
+	fun1()
+
+def fun3():
+	fun2()
+
+fun3()
+return "not reached"
+'
+	LANGUAGE plpythonu;
+SELECT nested_error_raise();
+ERROR:  plpy.Error: boom
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "nested_error_raise", line 10, in <module>
+    fun3()
+  PL/Python function "nested_error_raise", line 8, in fun3
+    fun2()
+  PL/Python function "nested_error_raise", line 5, in fun2
+    fun1()
+  PL/Python function "nested_error_raise", line 2, in fun1
+    raise plpy.Error("boom")
+PL/Python function "nested_error_raise"
+/* using plpy.warning should not produce a traceback
+*/
+CREATE FUNCTION nested_warning() RETURNS text
+	AS
+'def fun1():
+	plpy.warning("boom")
+
+def fun2():
+	fun1()
+
+def fun3():
+	fun2()
+
+fun3()
+return "you''ve been warned"
+'
+	LANGUAGE plpythonu;
+SELECT nested_warning();
+WARNING:  boom
+CONTEXT:  PL/Python function "nested_warning"
+   nested_warning   
+--------------------
+ you've been warned
+(1 row)
+
+/* AttributeError at toplevel used to give segfaults with the traceback
+*/
+CREATE FUNCTION toplevel_attribute_error() RETURNS void AS
+$$
+plpy.nonexistent
+$$ LANGUAGE plpythonu;
+SELECT toplevel_attribute_error();
+ERROR:  AttributeError: 'module' object has no attribute 'nonexistent'
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "toplevel_attribute_error", line 2, in <module>
+    plpy.nonexistent
+PL/Python function "toplevel_attribute_error"
+/* Calling PL/Python functions from SQL and vice versa should not lose context.
+ */
+CREATE OR REPLACE FUNCTION python_traceback() RETURNS void AS $$
+def first():
+  second()
+
+def second():
+  third()
+
+def third():
+  plpy.execute("select sql_error()")
+
+first()
+$$ LANGUAGE plpythonu;
+CREATE OR REPLACE FUNCTION sql_error() RETURNS void AS $$
+begin
+  select 1/0;
+end
+$$ LANGUAGE plpgsql;
+CREATE OR REPLACE FUNCTION python_from_sql_error() RETURNS void AS $$
+begin
+  select python_traceback();
+end
+$$ LANGUAGE plpgsql;
+CREATE OR REPLACE FUNCTION sql_from_python_error() RETURNS void AS $$
+plpy.execute("select sql_error()")
+$$ LANGUAGE plpythonu;
+SELECT python_traceback();
+ERROR:  spiexceptions.DivisionByZero: division by zero
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "python_traceback", line 11, in <module>
+    first()
+  PL/Python function "python_traceback", line 3, in first
+    second()
+  PL/Python function "python_traceback", line 6, in second
+    third()
+  PL/Python function "python_traceback", line 9, in third
+    plpy.execute("select sql_error()")
+PL/Python function "python_traceback"
+SELECT sql_error();
+ERROR:  division by zero
+CONTEXT:  SQL statement "select 1/0"
+PL/pgSQL function "sql_error" line 3 at SQL statement
+SELECT python_from_sql_error();
+ERROR:  spiexceptions.DivisionByZero: division by zero
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "python_traceback", line 11, in <module>
+    first()
+  PL/Python function "python_traceback", line 3, in first
+    second()
+  PL/Python function "python_traceback", line 6, in second
+    third()
+  PL/Python function "python_traceback", line 9, in third
+    plpy.execute("select sql_error()")
+PL/Python function "python_traceback"
+SQL statement "select python_traceback()"
+PL/pgSQL function "python_from_sql_error" line 3 at SQL statement
+SELECT sql_from_python_error();
+ERROR:  spiexceptions.DivisionByZero: division by zero
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "sql_from_python_error", line 2, in <module>
+    plpy.execute("select sql_error()")
+PL/Python function "sql_from_python_error"
 /* check catching specific types of exceptions
  */
 CREATE TABLE specific (
@@ -187,7 +360,10 @@ plpy.execute("rollback to save")
 $$ LANGUAGE plpythonu;
 SELECT manual_subxact();
 ERROR:  plpy.SPIError: SPI_execute failed: SPI_ERROR_TRANSACTION
-CONTEXT:  PL/Python function "manual_subxact"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "manual_subxact", line 2, in <module>
+    plpy.execute("savepoint save")
+PL/Python function "manual_subxact"
 /* same for prepared plans
  */
 CREATE FUNCTION manual_subxact_prepared() RETURNS void AS $$
@@ -199,4 +375,7 @@ plpy.execute(rollback)
 $$ LANGUAGE plpythonu;
 SELECT manual_subxact_prepared();
 ERROR:  plpy.SPIError: SPI_execute_plan failed: SPI_ERROR_TRANSACTION
-CONTEXT:  PL/Python function "manual_subxact_prepared"
+CONTEXT:  Traceback (most recent call last):
+  PL/Python function "manual_subxact_prepared", line 4, in <module>
+    plpy.execute(save)
+PL/Python function "manual_subxact_prepared"