Improvements to GetErrorContextStack()

As GetErrorContextStack() borrowed setup and tear-down code from other
places, it was less than clear that it must only be called as a
top-level entry point into the error system and can't be called by an
exception handler (unlike the rest of the error system, which is set up
to be reentrant-safe).

Being called from an exception handler is outside the charter of
GetErrorContextStack(), so add a bit more protection against it,
improve the comments addressing why we have to set up an errordata
stack for this function at all, and add a few more regression tests.

Lack of clarity pointed out by Tom Lane; all bugs are mine.

2 files changed, 68 insertions, 12 deletions

diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index 4394a3a1a7a..b022530ae4a 100644
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -4904,27 +4904,55 @@ declare _context text;
 begin
   get diagnostics _context = pg_context;
   raise notice '***%***', _context;
+  -- lets do it again, just for fun..
+  get diagnostics _context = pg_context;
+  raise notice '***%***', _context;
+  raise notice 'lets make sure we didnt break anything';
   return 2 * $1;
 end;
 $$ language plpgsql;
 create or replace function outer_func(int)
 returns int as $$
+declare
+  myresult int;
 begin
-  return inner_func($1);
+  raise notice 'calling down into inner_func()';
+  myresult := inner_func($1);
+  raise notice 'inner_func() done';
+  return myresult;
 end;
 $$ language plpgsql;
 create or replace function outer_outer_func(int)
 returns int as $$
+declare
+  myresult int;
 begin
-  return outer_func($1);
+  raise notice 'calling down into outer_func()';
+  myresult := outer_func($1);
+  raise notice 'outer_func() done';
+  return myresult;
 end;
 $$ language plpgsql;
 select outer_outer_func(10);
+NOTICE:  calling down into outer_func()
+NOTICE:  calling down into inner_func()
+CONTEXT:  PL/pgSQL function outer_outer_func(integer) line 6 at assignment
 NOTICE:  ***PL/pgSQL function inner_func(integer) line 4 at GET DIAGNOSTICS
-PL/pgSQL function outer_func(integer) line 3 at RETURN
-PL/pgSQL function outer_outer_func(integer) line 3 at RETURN***
-CONTEXT:  PL/pgSQL function outer_func(integer) line 3 at RETURN
-PL/pgSQL function outer_outer_func(integer) line 3 at RETURN
+PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment***
+CONTEXT:  PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  ***PL/pgSQL function inner_func(integer) line 7 at GET DIAGNOSTICS
+PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment***
+CONTEXT:  PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  lets make sure we didnt break anything
+CONTEXT:  PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  inner_func() done
+CONTEXT:  PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  outer_func() done
  outer_outer_func 
 ------------------
                20
@@ -4932,11 +4960,25 @@ PL/pgSQL function outer_outer_func(integer) line 3 at RETURN
 
 -- repeated call should to work
 select outer_outer_func(20);
+NOTICE:  calling down into outer_func()
+NOTICE:  calling down into inner_func()
+CONTEXT:  PL/pgSQL function outer_outer_func(integer) line 6 at assignment
 NOTICE:  ***PL/pgSQL function inner_func(integer) line 4 at GET DIAGNOSTICS
-PL/pgSQL function outer_func(integer) line 3 at RETURN
-PL/pgSQL function outer_outer_func(integer) line 3 at RETURN***
-CONTEXT:  PL/pgSQL function outer_func(integer) line 3 at RETURN
-PL/pgSQL function outer_outer_func(integer) line 3 at RETURN
+PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment***
+CONTEXT:  PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  ***PL/pgSQL function inner_func(integer) line 7 at GET DIAGNOSTICS
+PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment***
+CONTEXT:  PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  lets make sure we didnt break anything
+CONTEXT:  PL/pgSQL function outer_func(integer) line 6 at assignment
+PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  inner_func() done
+CONTEXT:  PL/pgSQL function outer_outer_func(integer) line 6 at assignment
+NOTICE:  outer_func() done
  outer_outer_func 
 ------------------
                40
diff --git a/src/test/regress/sql/plpgsql.sql b/src/test/regress/sql/plpgsql.sql
index b59715267e6..e791efadfdc 100644
--- a/src/test/regress/sql/plpgsql.sql
+++ b/src/test/regress/sql/plpgsql.sql
@@ -3888,21 +3888,35 @@ declare _context text;
 begin
   get diagnostics _context = pg_context;
   raise notice '***%***', _context;
+  -- lets do it again, just for fun..
+  get diagnostics _context = pg_context;
+  raise notice '***%***', _context;
+  raise notice 'lets make sure we didnt break anything';
   return 2 * $1;
 end;
 $$ language plpgsql;
 
 create or replace function outer_func(int)
 returns int as $$
+declare
+  myresult int;
 begin
-  return inner_func($1);
+  raise notice 'calling down into inner_func()';
+  myresult := inner_func($1);
+  raise notice 'inner_func() done';
+  return myresult;
 end;
 $$ language plpgsql;
 
 create or replace function outer_outer_func(int)
 returns int as $$
+declare
+  myresult int;
 begin
-  return outer_func($1);
+  raise notice 'calling down into outer_func()';
+  myresult := outer_func($1);
+  raise notice 'outer_func() done';
+  return myresult;
 end;
 $$ language plpgsql;