# Library(prolog\_coverage) - would like to see into call/1 when used, e.g. catch/3 **URL:** \ **Category:** General\ **Created:** [December 7, 2025, 9:37pm UTC](https://swi-prolog.discourse.group/t/library-prolog-coverage-would-like-to-see-into-call-1-when-used-e-g-catch-3/9421 "2025-12-07T21:37:37Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\ **Post date:** [December 7, 2025, 9:37pm UTC](https://swi-prolog.discourse.group/t/library-prolog-coverage-would-like-to-see-into-call-1-when-used-e-g-catch-3/9421/1 "2025-12-07T21:37:37Z")
$ swipl --version SWI-Prolog version 10.0.0 for x64-win64 Currently using [library(prolog\_coverage)](https://www.swi-prolog.org/pldoc/man?section=prologcoverage). For predicates like catch/3, which reference call/1 in their documentation (with the [reality](https://www.swi-prolog.org/pldoc/doc/_SWI_/boot/init.pl?show=src#catch/3) not being so apparent), the coverage report doesn’t capture the details of how call/1 is used. I realize this may be difficult—or even impossible—to implement, so I’m wondering if there might be a way to simulate such behavior to test both success and failure cases during testing. Actual report ```prolog 341 ++15 catch( 342 ( find_prolog_files('fixtures', Files), 343 is_list(Files) 344 ), 345 _, 346 true 347 ). ``` Something like the following is desired. ```prolog 341 ++15 catch( 342 ++15 ( find_prolog_files('fixtures', Files), 343 ++12 is_list(Files) 344 ), 345 _, 346 ++3 true 347 ). ``` ---
**Author:** ![jan](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/jan/32/4_2.png) [@jan](https://swi-prolog.discourse.group/u/jan)\ **Post date:** [December 8, 2025, 8:54am UTC](https://swi-prolog.discourse.group/t/library-prolog-coverage-would-like-to-see-into-call-1-when-used-e-g-catch-3/9421/2 "2025-12-08T08:54:47Z")
The success of the catch/3 basically confirms the success of what it calls 🙂 But no, at the moment there is no proper position support for meta-calling. Would be nice to have as it would also improve the debugger. Not easy to implement though ☹ For good debugging support I advice to avoid complex meta-calls, i.e., use a helper predicate. This is also faster. The system can be asked to do this transformation automatically, but this too looses source location information. Maybe there is a solution there by faking the source location information of the generated clause to reflect the positions from the meta-call … ---
**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\ **Post date:** [December 9, 2025, 5:20pm UTC](https://swi-prolog.discourse.group/t/library-prolog-coverage-would-like-to-see-into-call-1-when-used-e-g-catch-3/9421/3 "2025-12-09T17:20:10Z")
This is a step in the right direction, at least for my need. ```prolog 123 %% persist_assert_pred_def(+Name, +Arity, +Module, +File, +Line) 124 % Safely persists pred_def with duplicate detection and error handling 125 % persist_assert_pred_def(Name, Arity, Module, File, Line) :- 126 % catch( 127 % ( % Check if already exists (duplicate detection) 128 % ( pred_def(Name, Arity, Module, File, Line) 129 % -> % Already exists - log warning and succeed 130 % log_warning(debug_kb_consistency, 131 % duplicate_found(pred_def(Name, Arity, Module, File, Line))) 132 % ; % Not a duplicate - proceed with assertion 133 % % Log the intent to assert 134 % log_debug(debug_kb_assert, 135 % pred_def(Name, Arity, Module, File, Line)), 136 % % Use auto-generated persist predicate 137 % assert_pred_def(Name, Arity, Module, File, Line) 138 % ) 139 % ), 140 % Error, 141 % % Log failure and re-throw 142 % ( log_error(debug_kb_assert, 143 % operation_failed(pred_def(Name, Arity, Module, File, Line), Error)), 144 % throw(Error) 145 % ) 146 % ). 147 148 ++55,870 persist_assert_pred_def(Name, Arity, Module, File, Line) :- 149 ++55,870 catch( 150 goal_a_success(Name, Arity, Module, File, Line), 151 Error, 152 goal_a_failure(Name, Arity, Module, File, Line, Error) 153 ). 154 155 ++55,870 goal_a_success(Name, Arity, Module, File, Line) :- 156 ( % Check if already exists (duplicate detection) 157 +20-55,850 ( pred_def(Name, Arity, Module, File, Line) 158 -> % Already exists - log warning and succeed 159 ++20 log_warning(debug_kb_consistency, 160 duplicate_found(pred_def(Name, Arity, Module, File, Line))) 161 ; % Not a duplicate - proceed with assertion 162 % Log the intent to assert 163 ++55,850 log_debug(debug_kb_assert, 164 pred_def(Name, Arity, Module, File, Line)), 165 % Use auto-generated persist predicate 166 ++55,850 assert_pred_def(Name, Arity, Module, File, Line) 167 ) 168 ). 169 170 ### goal_a_failure(Name, Arity, Module, File, Line, Error) :- 171 % Log failure and re-throw 172 ( log_error(debug_kb_assert, 173 operation_failed(pred_def(Name, Arity, Module, File, Line), Error)), 174 throw(Error) 175 ). ```