Improve regression tests' code coverage for plpgsql control structures.

I noticed that our code coverage report showed considerable deficiency
in test coverage for PL/pgSQL control statements.  Notably, both
exec_stmt_block and most of the loop control statements had very poor
coverage of handling of return/exit/continue result codes from their
child statements; and exec_stmt_fori was seriously lacking in feature
coverage, having no test that exercised its BY or REVERSE features,
nor verification that its overflow defenses work.

Now that we have some infrastructure for plpgsql-specific test scripts,
the natural thing to do is make a new script rather than further extend
plpgsql.sql.  So I created a new script plpgsql_control.sql with the
charter to test plpgsql control structures, and moved a few existing
tests there because they fell entirely under that charter.  I then
added new test cases that exercise the bits of code complained of above.

Of the five kinds of loop statements, only exec_stmt_while's result code
handling is fully exercised by these tests.  That would be a deficiency
as things stand, but a follow-on commit will merge the loop statements'
result code handling into one implementation.  So testing each usage of
that implementation separately seems redundant.

In passing, also add a couple test cases to plpgsql.sql to more fully
exercise plpgsql's code related to expanded arrays --- I had thought
that area was sufficiently covered already, but the coverage report
showed a couple of un-executed code paths.

Discussion: https://postgr.es/m/26314.1514670401@sss.pgh.pa.us

src/pl/plpgsql/src/Makefile

@@ -26,7 +26,7 @@ DATA = plpgsql.control plpgsql--1.0.sql plpgsql--unpackaged--1.0.sql
 
 REGRESS_OPTS = --dbname=$(PL_TESTDB)
 
-REGRESS = plpgsql_call
+REGRESS = plpgsql_call plpgsql_control
 
 all: all-lib
 

src/test/regress/sql/plpgsql.sql

@@ -2285,241 +2285,6 @@ end;$$ language plpgsql;
 select raise_exprs();
 drop function raise_exprs();
 
--- continue statement
-create table conttesttbl(idx serial, v integer);
-insert into conttesttbl(v) values(10);
-insert into conttesttbl(v) values(20);
-insert into conttesttbl(v) values(30);
-insert into conttesttbl(v) values(40);
-
-create function continue_test1() returns void as $$
-declare _i integer = 0; _r record;
-begin
-  raise notice '---1---';
-  loop
-    _i := _i + 1;
-    raise notice '%', _i;
-    continue when _i < 10;
-    exit;
-  end loop;
-
-  raise notice '---2---';
-  <<lbl>>
-  loop
-    _i := _i - 1;
-    loop
-      raise notice '%', _i;
-      continue lbl when _i > 0;
-      exit lbl;
-    end loop;
-  end loop;
-
-  raise notice '---3---';
-  <<the_loop>>
-  while _i < 10 loop
-    _i := _i + 1;
-    continue the_loop when _i % 2 = 0;
-    raise notice '%', _i;
-  end loop;
-
-  raise notice '---4---';
-  for _i in 1..10 loop
-    begin
-      -- applies to outer loop, not the nested begin block
-      continue when _i < 5;
-      raise notice '%', _i;
-    end;
-  end loop;
-
-  raise notice '---5---';
-  for _r in select * from conttesttbl loop
-    continue when _r.v <= 20;
-    raise notice '%', _r.v;
-  end loop;
-
-  raise notice '---6---';
-  for _r in execute 'select * from conttesttbl' loop
-    continue when _r.v <= 20;
-    raise notice '%', _r.v;
-  end loop;
-
-  raise notice '---7---';
-  for _i in 1..3 loop
-    raise notice '%', _i;
-    continue when _i = 3;
-  end loop;
-
-  raise notice '---8---';
-  _i := 1;
-  while _i <= 3 loop
-    raise notice '%', _i;
-    _i := _i + 1;
-    continue when _i = 3;
-  end loop;
-
-  raise notice '---9---';
-  for _r in select * from conttesttbl order by v limit 1 loop
-    raise notice '%', _r.v;
-    continue;
-  end loop;
-
-  raise notice '---10---';
-  for _r in execute 'select * from conttesttbl order by v limit 1' loop
-    raise notice '%', _r.v;
-    continue;
-  end loop;
-end; $$ language plpgsql;
-
-select continue_test1();
-
-drop function continue_test1();
-drop table conttesttbl;
-
--- should fail: CONTINUE is only legal inside a loop
-create function continue_error1() returns void as $$
-begin
-    begin
-        continue;
-    end;
-end;
-$$ language plpgsql;
-
--- should fail: unlabeled EXIT is only legal inside a loop
-create function exit_error1() returns void as $$
-begin
-    begin
-        exit;
-    end;
-end;
-$$ language plpgsql;
-
--- should fail: no such label
-create function continue_error2() returns void as $$
-begin
-    begin
-        loop
-            continue no_such_label;
-        end loop;
-    end;
-end;
-$$ language plpgsql;
-
--- should fail: no such label
-create function exit_error2() returns void as $$
-begin
-    begin
-        loop
-            exit no_such_label;
-        end loop;
-    end;
-end;
-$$ language plpgsql;
-
--- should fail: CONTINUE can't reference the label of a named block
-create function continue_error3() returns void as $$
-begin
-    <<begin_block1>>
-    begin
-        loop
-            continue begin_block1;
-        end loop;
-    end;
-end;
-$$ language plpgsql;
-
--- On the other hand, EXIT *can* reference the label of a named block
-create function exit_block1() returns void as $$
-begin
-    <<begin_block1>>
-    begin
-        loop
-            exit begin_block1;
-            raise exception 'should not get here';
-        end loop;
-    end;
-end;
-$$ language plpgsql;
-
-select exit_block1();
-drop function exit_block1();
-
--- verbose end block and end loop
-create function end_label1() returns void as $$
-<<blbl>>
-begin
-  <<flbl1>>
-  for _i in 1 .. 10 loop
-    exit flbl1;
-  end loop flbl1;
-  <<flbl2>>
-  for _i in 1 .. 10 loop
-    exit flbl2;
-  end loop;
-end blbl;
-$$ language plpgsql;
-
-select end_label1();
-drop function end_label1();
-
--- should fail: undefined end label
-create function end_label2() returns void as $$
-begin
-  for _i in 1 .. 10 loop
-    exit;
-  end loop flbl1;
-end;
-$$ language plpgsql;
-
--- should fail: end label does not match start label
-create function end_label3() returns void as $$
-<<outer_label>>
-begin
-  <<inner_label>>
-  for _i in 1 .. 10 loop
-    exit;
-  end loop outer_label;
-end;
-$$ language plpgsql;
-
--- should fail: end label on a block without a start label
-create function end_label4() returns void as $$
-<<outer_label>>
-begin
-  for _i in 1 .. 10 loop
-    exit;
-  end loop outer_label;
-end;
-$$ language plpgsql;
-
--- using list of scalars in fori and fore stmts
-create function for_vect() returns void as $proc$
-<<lbl>>declare a integer; b varchar; c varchar; r record;
-begin
-  -- fori
-  for i in 1 .. 3 loop
-    raise notice '%', i;
-  end loop;
-  -- fore with record var
-  for r in select gs as aa, 'BB' as bb, 'CC' as cc from generate_series(1,4) gs loop
-    raise notice '% % %', r.aa, r.bb, r.cc;
-  end loop;
-  -- fore with single scalar
-  for a in select gs from generate_series(1,4) gs loop
-    raise notice '%', a;
-  end loop;
-  -- fore with multiple scalars
-  for a,b,c in select gs, 'BB','CC' from generate_series(1,4) gs loop
-    raise notice '% % %', a, b, c;
-  end loop;
-  -- using qualified names in fors, fore is enabled, disabled only for fori
-  for lbl.a, lbl.b, lbl.c in execute $$select gs, 'bb','cc' from generate_series(1,4) gs$$ loop
-    raise notice '% % %', a, b, c;
-  end loop;
-end;
-$proc$ language plpgsql;
-
-select for_vect();
-
 -- regression test: verify that multiple uses of same plpgsql datum within
 -- a SQL command all get mapped to the same $n parameter.  The return value
 -- of the SELECT is not important, we only care that it doesn't fail with
@@ -3580,72 +3345,6 @@ select stacked_diagnostics_test();
 
 drop function stacked_diagnostics_test();
 
--- test CASE statement
-
-create or replace function case_test(bigint) returns text as $$
-declare a int = 10;
-        b int = 1;
-begin
-  case $1
-    when 1 then
-      return 'one';
-    when 2 then
-      return 'two';
-    when 3,4,3+5 then
-      return 'three, four or eight';
-    when a then
-      return 'ten';
-    when a+b, a+b+1 then
-      return 'eleven, twelve';
-  end case;
-end;
-$$ language plpgsql immutable;
-
-select case_test(1);
-select case_test(2);
-select case_test(3);
-select case_test(4);
-select case_test(5); -- fails
-select case_test(8);
-select case_test(10);
-select case_test(11);
-select case_test(12);
-select case_test(13); -- fails
-
-create or replace function catch() returns void as $$
-begin
-  raise notice '%', case_test(6);
-exception
-  when case_not_found then
-    raise notice 'caught case_not_found % %', SQLSTATE, SQLERRM;
-end
-$$ language plpgsql;
-
-select catch();
-
--- test the searched variant too, as well as ELSE
-create or replace function case_test(bigint) returns text as $$
-declare a int = 10;
-begin
-  case
-    when $1 = 1 then
-      return 'one';
-    when $1 = a + 2 then
-      return 'twelve';
-    else
-      return 'other';
-  end case;
-end;
-$$ language plpgsql immutable;
-
-select case_test(1);
-select case_test(2);
-select case_test(12);
-select case_test(13);
-
-drop function catch();
-drop function case_test(bigint);
-
 -- test variadic functions
 
 create or replace function vari(variadic int[])
@@ -4278,6 +3977,8 @@ language plpgsql as $$
   begin return $1[1]; end;
 $$ stable;
 
+select consumes_rw_array(returns_rw_array(42));
+
 -- bug #14174
 explain (verbose, costs off)
 select i, a from
@@ -4300,6 +4001,13 @@ select consumes_rw_array(a), a from
 select consumes_rw_array(a), a from
   (values (returns_rw_array(1)), (returns_rw_array(2))) v(a);
 
+do $$
+declare a int[] := array[1,2];
+begin
+  a := a || 3;
+  raise notice 'a = %', a;
+end$$;
+
 
 --
 -- Test access to call stack