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This is really nice @dkcumming, I love the story in your commits. I feel strongly about including a test to surface regressions, as I expect there are many more features to come.
There are no integration or unit tests for the SKIP_LANG_START behavior. The existing .smir.json.expected files all contain lang_start items, so there's good data to work from. At minimum, an integration test that runs with SKIP_LANG_START=1 and verifies the output lacks lang_start entries would give confidence this doesn't regress.
This filters out all `lang_start` items (functions, closures, drop glue etc.). It only removes the items if they are `std::rt::lang_start` or are exclusively reachable by those functions. That means `black_box` is removed if it is not called otherwise in the program, but if it is then it is not removed. There is a couple of stages to get the data together in the right form so that only the items desired to be removed are.
Introduces an extensible ItemFilter enum so future exclusion predicates can be added by just adding a variant, wiring its env var in enabled(), and implementing compute_exclusions. The key behavioral change: apply_all() now prunes ctx.functions in addition to items, so ctx.resolve_call_target() returns None for excluded callees. This eliminates the need to thread an `excluded` set through every render function; both dot and d2 renderers are simplified.
Adds a `make test-skip-lang-start` target that runs every test program through the D2 renderer with SKIP_LANG_START=1 and verifies the output contains no lang_start references. Catches regressions in the ItemFilter pipeline without needing separate golden files.
…ring Replace if-let + early-return with match expression in filter_map, use matches! macro for single-arm boolean match, and switch enabled() from imperative push to declarative array-of-options pattern.
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The integration test now validates at the data-structure level instead of grepping rendered output. When ASSERT_FILTER=1 is set alongside SKIP_LANG_START=1, apply_all() asserts two things: 1. The filter's exclusion set is non-empty (precondition: lang_start items were present to begin with). 2. No matching items survive in the filtered output (postcondition: the filter actually worked). The precondition check is pedantically complete: std::rt::lang_start is the runtime wrapper rustc generates for every crate with a fn main, so it will always appear in monomorphized output. Every one of the 29 test programs has a main function and every expected output contains exactly 11 lang_start references. It would take a fundamental change to rustc's runtime initialization for this to stop being true; but if it does, the assertion will tell us the test data is stale rather than silently passing. The more realistic failure mode: someone adds a library crate (no main) to the test suite. The assert message spells this out and gives two actionable options (skip lib crates in the test target, or gate the filter on the presence of main).
echo's treatment of \n is shell-dependent (bash interprets it by default, zsh and POSIX sh do not without -e). Switch report() and the failure summary to printf in both integration-test and test-skip-lang-start targets.
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This PR allows us to set a
SKIP_LANG_START=1env var to remove thestd::rt::lang_startitems from the graph output. Perhaps sometimes they are useful, but I have not ever needed to look at them and would prefer them to be removed from the graph.I had a bit of trouble getting the correct items for the BFS and I used claude to help for full disclosure, however I have vetted the code and agree with it. Also the output has been tested and it does remove the items correctly. I will post before and after of a contrived program that contains
black_boxto show that the algorithm will only remove items exclusively downstream ofstd::rt::lang_start.Before
After