With it when using multiple Machine in one process only the first would store the pre-allocated error.
Instead Heap.resource_err_loc is now Option<NonZero<usize>> instead of usize using None for uninitialized.
The cell at index 0 should alredy be used by a runtime reserved interstitial cell that is allocated prior. So requiring the offset to be non zero should be fine.
- reserve the complete required length at the beginning to reduce reallocations
- use u8 instead of char so that we can re-use the allocation for the string
The -t flag is not limited to arity 0 predicates - it accepts any
goal including goals with arguments (e.g., -t 'halt(1)'). Updated
the help text to remove the incorrect "(arity 0 predicate)" constraint.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
Per maintainer feedback, switches must come before files to follow
the convention: switches before files are Scryer-specific, switches
after files are application-specific.
The custom_toplevel.pl unit tests were trivial and didn't actually test
the functionality. All real testing is done via comprehensive CLI tests
in tests/scryer/cli/src_tests/custom_toplevel.md
- Add dynamic directive in toplevel.pl with other module-level directives
- Update test files to reference it as '':g_caused_exception/2
- Remove redundant dynamic directives from test files
- All tests passing
Following TESTING_GUIDE.md, added tests at layers 2 and 3:
Layer 2 - Prolog Integration Tests (src/tests/custom_toplevel.pl):
- Test that g_caused_exception/2 is not asserted when no exception occurs
- Test that g_caused_exception/2 can be checked from custom toplevel
- Added check_for_exception/0 helper predicate for testing
Layer 3 - CLI Tests (tests/scryer/cli/src_tests/custom_toplevel.md):
- Test g_caused_exception/2 with exception thrown
- Test g_caused_exception/2 with no exception
- Test g_caused_exception/2 with error/2 terms
- Added test helper predicates in fixtures/toplevel_test_helper.pl
All tests pass successfully.
Co-Authored-By: J.J.'s Robot <jjtolton@gmail.com>
When a goal throws an exception during initialization (-g flag), the
system now asserts g_caused_exception(Goal, Exception) in the user
module. This allows custom toplevels (-t flag) to check if an error
occurred and handle it appropriately.
Example usage:
scryer-prolog -g "throw(error)" -t check_error
Where check_error can be:
:- dynamic(g_caused_exception/2).
check_error :-
( g_caused_exception(_, E) ->
write('Error: '), write(E), nl, halt(1)
; halt(0)
).
This enables scripts to use custom toplevels for sophisticated error
handling and exit code logic.
Addresses: https://github.com/mthom/scryer-prolog/pull/3147#issuecomment-3503875719
Co-Authored-By: J.J.'s Robot <jjtolton@gmail.com>
Fixed issue where `scryer-prolog -t halt` would try to load "halt.pl"
as a file instead of just using halt as the custom toplevel.
The bug was caused by an extra clause `delegate_task([], []).` that
would return control to the calling context instead of continuing to
start_toplevel. This caused the argument processing in delegate_task
to continue and treat the already-consumed toplevel argument as a
filename.
Removing this clause ensures that delegate_task([], Goals0) always
proceeds to load initialization files and start the toplevel, fixing
the double-processing bug.
Co-Authored-By: J.J.'s Robot <jjtolton@gmail.com>
- Create Prolog integration tests in src/tests/custom_toplevel.pl
- Add CLI test configuration in tests/scryer/cli/src_tests/custom_toplevel_tests.toml
- Tests verify:
* -t halt terminates after initialization
* Custom toplevels can be user-defined predicates
* Toplevel receives control after initialization completes
* Default behavior is REPL when no -t specified
- All tests pass successfully
Following TESTING_GUIDE.md three-layer testing approach:
- Layer 2: Prolog integration tests with test_framework
- Layer 3: CLI snapshot tests with .toml configuration
Co-Authored-By: J.J.'s Robot <noreply@example.com>
- Add -t FLAG to specify custom toplevel (arity 0 predicate)
- Default toplevel is 'repl' if -t is not specified
- Using `-t halt` achieves original goal of guaranteed termination
- Custom toplevels enable flexible exit strategies (e.g., server mode)
- Update help text to document -t flag
Examples:
scryer-prolog -t halt program.pl # Exits after execution
scryer-prolog -t my_repl program.pl # Custom REPL
scryer-prolog program.pl # Default REPL
Co-Authored-By: J.J.'s Robot <noreply@example.com>
