Submitted by: @pavel-zotov

Attachments:
missed-comments-to-sp-parameters-when-extract-metadata.7z

Consider script:

set bail on;
shell del C:\temp\tmp.fdb 2>nul;
create database 'localhost:C:\temp\tmp.fdb';
set term ^;
create or alter procedure sp_1(
p00 int -- single-line comment for `p00`
,p01 int
/*
multi-line comment
for `p01`,
typed on
several
lines
*/
,p02 int /* multi-line comment for `p02`, typed in one line */
,p03 varchar(1) character set utf8 -- single line comment for `p03` which has `character set` clause
,p04 type of column rdb$database.rdb$relation_id /* multi-line comment for `p04` which has `type of column` clause */
,
p05 int default null -- p05
-- ^^^^^^^
,
p06 int = null /* p06 */
-- ^
) returns (
r01 int -- r01
,r02 char(1) not null /* r02 */
)
as
begin
-- nop --
end
^
set term ;^
commit;

(it can be seen more readable in attached .7z / .png).

If we run 'isql -x' for this DB then extracted metadata SQL will be like this:

SET TERM ^ ;

/* Stored procedures headers */
CREATE OR ALTER PROCEDURE SP_1 (P00 INTEGER,
P01 INTEGER,
P02 INTEGER,
P03 VARCHAR(1) CHARACTER SET UTF8,
P04 TYPE OF COLUMN RDB$DATABASE.RDB$RELATION_ID,
P05 INTEGER default null -- p05
-- ^^^^^^^
,
P06 INTEGER = null /* p06 */
-- ^
)
RETURNS (R01 INTEGER,
R02 CHAR(1) CHARACTER SET NONE NOT NULL)
AS
BEGIN EXIT; END ^

SET TERM ; ^
COMMIT WORK;
SET AUTODDL ON;

COMMIT WORK;
SET AUTODDL OFF;
SET TERM ^ ;

/* Stored procedures bodies */

ALTER PROCEDURE SP_1 (P00 INTEGER,
P01 INTEGER,
P02 INTEGER,
P03 VARCHAR(1) CHARACTER SET UTF8,
P04 TYPE OF COLUMN RDB$DATABASE.RDB$RELATION_ID,
P05 INTEGER default null -- p05
-- ^^^^^^^
,
P06 INTEGER = null /* p06 */
-- ^
)
RETURNS (R01 INTEGER,
R02 CHAR(1) CHARACTER SET NONE NOT NULL)
AS
begin
-- nop --
end ^

SET TERM ; ^

So, comments for any input parameter will be lost if this pareameter was declared WITHOUT 'default' or '=' modifier.
Comments for output parameters will be lost at all.

Checked on:
WI-V4.0.0.2399
WI-V3.0.8.33431

FB 2.5 can not be used here: it does not preserve any comments of this type.

PS.
Priority was set to minor. This "feature" can be considered as inconvenience rather than real bug.