compiler/rustc_builtin_macros/src/test_harness.rs

   1 // Code that generates a test runner to run all the tests in a crate
   2
   3 use rustc_ast as ast;
   4 use rustc_ast::entry::EntryPointType;
   5 use rustc_ast::mut_visit::{ExpectOne, *};
   6 use rustc_ast::ptr::P;
   7 use rustc_ast::{attr, ModKind};
   8 use rustc_expand::base::{ExtCtxt, ResolverExpand};
   9 use rustc_expand::expand::{AstFragment, ExpansionConfig};
  10 use rustc_feature::Features;
  11 use rustc_session::Session;
  12 use rustc_span::hygiene::{AstPass, SyntaxContext, Transparency};
  13 use rustc_span::symbol::{sym, Ident, Symbol};
  14 use rustc_span::{Span, DUMMY_SP};
  15 use rustc_target::spec::PanicStrategy;
  16 use smallvec::{smallvec, SmallVec};
  17 use tracing::debug;
  18
  19 use std::{iter, mem};
  20
  21 struct Test {
  22     span: Span,
  23     ident: Ident,
  24 }
  25
  26 struct TestCtxt<'a> {
  27     ext_cx: ExtCtxt<'a>,
  28     panic_strategy: PanicStrategy,
  29     def_site: Span,
  30     test_cases: Vec<Test>,
  31     reexport_test_harness_main: Option<Symbol>,
  32     test_runner: Option<ast::Path>,
  33 }
  34
  35 // Traverse the crate, collecting all the test functions, eliding any
  36 // existing main functions, and synthesizing a main test harness
  37 pub fn inject(sess: &Session, resolver: &mut dyn ResolverExpand, krate: &mut ast::Crate) {
  38     let span_diagnostic = sess.diagnostic();
  39     let panic_strategy = sess.panic_strategy();
  40     let platform_panic_strategy = sess.target.panic_strategy;
  41
  42     // Check for #![reexport_test_harness_main = "some_name"] which gives the
  43     // main test function the name `some_name` without hygiene. This needs to be
  44     // unconditional, so that the attribute is still marked as used in
  45     // non-test builds.
  46     let reexport_test_harness_main =
  47         sess.first_attr_value_str_by_name(&krate.attrs, sym::reexport_test_harness_main);
  48
  49     // Do this here so that the test_runner crate attribute gets marked as used
  50     // even in non-test builds
  51     let test_runner = get_test_runner(sess, span_diagnostic, &krate);
  52
  53     if sess.opts.test {
  54         let panic_strategy = match (panic_strategy, sess.opts.debugging_opts.panic_abort_tests) {
  55             (PanicStrategy::Abort, true) => PanicStrategy::Abort,
  56             (PanicStrategy::Abort, false) => {
  57                 if panic_strategy == platform_panic_strategy {
  58                     // Silently allow compiling with panic=abort on these platforms,
  59                     // but with old behavior (abort if a test fails).
  60                 } else {
  61                     span_diagnostic.err(
  62                         "building tests with panic=abort is not supported \
  63                                          without `-Zpanic_abort_tests`",
  64                     );
  65                 }
  66                 PanicStrategy::Unwind
  67             }
  68             (PanicStrategy::Unwind, _) => PanicStrategy::Unwind,
  69         };
  70         generate_test_harness(
  71             sess,
  72             resolver,
  73             reexport_test_harness_main,
  74             krate,
  75             &sess.features_untracked(),
  76             panic_strategy,
  77             test_runner,
  78         )
  79     }
  80 }
  81
  82 struct TestHarnessGenerator<'a> {
  83     cx: TestCtxt<'a>,
  84     tests: Vec<Test>,
  85 }
  86
  87 impl<'a> MutVisitor for TestHarnessGenerator<'a> {
  88     fn visit_crate(&mut self, c: &mut ast::Crate) {
  89         noop_visit_crate(c, self);
  90
  91         // Create a main function to run our tests
  92         c.items.push(mk_main(&mut self.cx));
  93     }
  94
  95     fn flat_map_item(&mut self, i: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
  96         let mut item = i.into_inner();
  97         if is_test_case(&self.cx.ext_cx.sess, &item) {
  98             debug!("this is a test item");
  99
 100             let test = Test { span: item.span, ident: item.ident };
 101             self.tests.push(test);
 102         }
 103
 104         // We don't want to recurse into anything other than mods, since
 105         // mods or tests inside of functions will break things
 106         if let ast::ItemKind::Mod(..) = item.kind {
 107             let tests = mem::take(&mut self.tests);
 108             noop_visit_item_kind(&mut item.kind, self);
 109             let mut tests = mem::replace(&mut self.tests, tests);
 110
 111             if !tests.is_empty() {
 112                 let parent =
 113                     if item.id == ast::DUMMY_NODE_ID { ast::CRATE_NODE_ID } else { item.id };
 114                 // Create an identifier that will hygienically resolve the test
 115                 // case name, even in another module.
 116                 let inner_span = match item.kind {
 117                     ast::ItemKind::Mod(_, ModKind::Loaded(.., span)) => span,
 118                     _ => unreachable!(),
 119                 };
 120                 let expn_id = self.cx.ext_cx.resolver.expansion_for_ast_pass(
 121                     inner_span,
 122                     AstPass::TestHarness,
 123                     &[],
 124                     Some(parent),
 125                 );
 126                 for test in &mut tests {
 127                     // See the comment on `mk_main` for why we're using
 128                     // `apply_mark` directly.
 129                     test.ident.span = test.ident.span.apply_mark(expn_id, Transparency::Opaque);
 130                 }
 131                 self.cx.test_cases.extend(tests);
 132             }
 133         }
 134         smallvec![P(item)]
 135     }
 136 }
 137
 138 // Beware, this is duplicated in librustc_passes/entry.rs (with
 139 // `rustc_hir::Item`), so make sure to keep them in sync.
 140 fn entry_point_type(sess: &Session, item: &ast::Item, depth: usize) -> EntryPointType {
 141     match item.kind {
 142         ast::ItemKind::Fn(..) => {
 143             if sess.contains_name(&item.attrs, sym::start) {
 144                 EntryPointType::Start
 145             } else if sess.contains_name(&item.attrs, sym::main) {
 146                 EntryPointType::MainAttr
 147             } else if item.ident.name == sym::main {
 148                 if depth == 1 {
 149                     // This is a top-level function so can be 'main'
 150                     EntryPointType::MainNamed
 151                 } else {
 152                     EntryPointType::OtherMain
 153                 }
 154             } else {
 155                 EntryPointType::None
 156             }
 157         }
 158         _ => EntryPointType::None,
 159     }
 160 }
 161 /// A folder used to remove any entry points (like fn main) because the harness
 162 /// generator will provide its own
 163 struct EntryPointCleaner<'a> {
 164     // Current depth in the ast
 165     sess: &'a Session,
 166     depth: usize,
 167     def_site: Span,
 168 }
 169
 170 impl<'a> MutVisitor for EntryPointCleaner<'a> {
 171     fn flat_map_item(&mut self, i: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
 172         self.depth += 1;
 173         let item = noop_flat_map_item(i, self).expect_one("noop did something");
 174         self.depth -= 1;
 175
 176         // Remove any #[main] or #[start] from the AST so it doesn't
 177         // clash with the one we're going to add, but mark it as
 178         // #[allow(dead_code)] to avoid printing warnings.
 179         let item = match entry_point_type(self.sess, &item, self.depth) {
 180             EntryPointType::MainNamed | EntryPointType::MainAttr | EntryPointType::Start => item
 181                 .map(|ast::Item { id, ident, attrs, kind, vis, span, tokens }| {
 182                     let allow_ident = Ident::new(sym::allow, self.def_site);
 183                     let dc_nested =
 184                         attr::mk_nested_word_item(Ident::new(sym::dead_code, self.def_site));
 185                     let allow_dead_code_item = attr::mk_list_item(allow_ident, vec![dc_nested]);
 186                     let allow_dead_code = attr::mk_attr_outer(allow_dead_code_item);
 187                     let attrs = attrs
 188                         .into_iter()
 189                         .filter(|attr| {
 190                             !self.sess.check_name(attr, sym::main)
 191                                 && !self.sess.check_name(attr, sym::start)
 192                         })
 193                         .chain(iter::once(allow_dead_code))
 194                         .collect();
 195
 196                     ast::Item { id, ident, attrs, kind, vis, span, tokens }
 197                 }),
 198             EntryPointType::None | EntryPointType::OtherMain => item,
 199         };
 200
 201         smallvec![item]
 202     }
 203 }
 204
 205 /// Crawl over the crate, inserting test reexports and the test main function
 206 fn generate_test_harness(
 207     sess: &Session,
 208     resolver: &mut dyn ResolverExpand,
 209     reexport_test_harness_main: Option<Symbol>,
 210     krate: &mut ast::Crate,
 211     features: &Features,
 212     panic_strategy: PanicStrategy,
 213     test_runner: Option<ast::Path>,
 214 ) {
 215     let mut econfig = ExpansionConfig::default("test".to_string());
 216     econfig.features = Some(features);
 217
 218     let ext_cx = ExtCtxt::new(sess, econfig, resolver, None);
 219
 220     let expn_id = ext_cx.resolver.expansion_for_ast_pass(
 221         DUMMY_SP,
 222         AstPass::TestHarness,
 223         &[sym::main, sym::test, sym::rustc_attrs],
 224         None,
 225     );
 226     let def_site = DUMMY_SP.with_def_site_ctxt(expn_id);
 227
 228     // Remove the entry points
 229     let mut cleaner = EntryPointCleaner { sess, depth: 0, def_site };
 230     cleaner.visit_crate(krate);
 231
 232     let cx = TestCtxt {
 233         ext_cx,
 234         panic_strategy,
 235         def_site,
 236         test_cases: Vec::new(),
 237         reexport_test_harness_main,
 238         test_runner,
 239     };
 240
 241     TestHarnessGenerator { cx, tests: Vec::new() }.visit_crate(krate);
 242 }
 243
 244 /// Creates a function item for use as the main function of a test build.
 245 /// This function will call the `test_runner` as specified by the crate attribute
 246 ///
 247 /// By default this expands to
 248 ///
 249 /// ```
 250 /// #[main]
 251 /// pub fn main() {
 252 ///     extern crate test;
 253 ///     test::test_main_static(&[
 254 ///         &test_const1,
 255 ///         &test_const2,
 256 ///         &test_const3,
 257 ///     ]);
 258 /// }
 259 /// ```
 260 ///
 261 /// Most of the Ident have the usual def-site hygiene for the AST pass. The
 262 /// exception is the `test_const`s. These have a syntax context that has two
 263 /// opaque marks: one from the expansion of `test` or `test_case`, and one
 264 /// generated  in `TestHarnessGenerator::flat_map_item`. When resolving this
 265 /// identifier after failing to find a matching identifier in the root module
 266 /// we remove the outer mark, and try resolving at its def-site, which will
 267 /// then resolve to `test_const`.
 268 ///
 269 /// The expansion here can be controlled by two attributes:
 270 ///
 271 /// [`TestCtxt::reexport_test_harness_main`] provides a different name for the `main`
 272 /// function and [`TestCtxt::test_runner`] provides a path that replaces
 273 /// `test::test_main_static`.
 274 fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
 275     let sp = cx.def_site;
 276     let ecx = &cx.ext_cx;
 277     let test_id = Ident::new(sym::test, sp);
 278
 279     let runner_name = match cx.panic_strategy {
 280         PanicStrategy::Unwind => "test_main_static",
 281         PanicStrategy::Abort => "test_main_static_abort",
 282     };
 283
 284     // test::test_main_static(...)
 285     let mut test_runner = cx
 286         .test_runner
 287         .clone()
 288         .unwrap_or_else(|| ecx.path(sp, vec![test_id, Ident::from_str_and_span(runner_name, sp)]));
 289
 290     test_runner.span = sp;
 291
 292     let test_main_path_expr = ecx.expr_path(test_runner);
 293     let call_test_main = ecx.expr_call(sp, test_main_path_expr, vec![mk_tests_slice(cx, sp)]);
 294     let call_test_main = ecx.stmt_expr(call_test_main);
 295
 296     // extern crate test
 297     let test_extern_stmt =
 298         ecx.stmt_item(sp, ecx.item(sp, test_id, vec![], ast::ItemKind::ExternCrate(None)));
 299
 300     // #[main]
 301     let main_meta = ecx.meta_word(sp, sym::main);
 302     let main_attr = ecx.attribute(main_meta);
 303
 304     // pub fn main() { ... }
 305     let main_ret_ty = ecx.ty(sp, ast::TyKind::Tup(vec![]));
 306
 307     // If no test runner is provided we need to import the test crate
 308     let main_body = if cx.test_runner.is_none() {
 309         ecx.block(sp, vec![test_extern_stmt, call_test_main])
 310     } else {
 311         ecx.block(sp, vec![call_test_main])
 312     };
 313
 314     let decl = ecx.fn_decl(vec![], ast::FnRetTy::Ty(main_ret_ty));
 315     let sig = ast::FnSig { decl, header: ast::FnHeader::default(), span: sp };
 316     let def = ast::Defaultness::Final;
 317     let main =
 318         ast::ItemKind::Fn(box ast::FnKind(def, sig, ast::Generics::default(), Some(main_body)));
 319
 320     // Honor the reexport_test_harness_main attribute
 321     let main_id = match cx.reexport_test_harness_main {
 322         Some(sym) => Ident::new(sym, sp.with_ctxt(SyntaxContext::root())),
 323         None => Ident::new(sym::main, sp),
 324     };
 325
 326     let main = P(ast::Item {
 327         ident: main_id,
 328         attrs: vec![main_attr],
 329         id: ast::DUMMY_NODE_ID,
 330         kind: main,
 331         vis: ast::Visibility { span: sp, kind: ast::VisibilityKind::Public, tokens: None },
 332         span: sp,
 333         tokens: None,
 334     });
 335
 336     // Integrate the new item into existing module structures.
 337     let main = AstFragment::Items(smallvec![main]);
 338     cx.ext_cx.monotonic_expander().fully_expand_fragment(main).make_items().pop().unwrap()
 339 }
 340
 341 /// Creates a slice containing every test like so:
 342 /// &[&test1, &test2]
 343 fn mk_tests_slice(cx: &TestCtxt<'_>, sp: Span) -> P<ast::Expr> {
 344     debug!("building test vector from {} tests", cx.test_cases.len());
 345     let ecx = &cx.ext_cx;
 346
 347     ecx.expr_vec_slice(
 348         sp,
 349         cx.test_cases
 350             .iter()
 351             .map(|test| {
 352                 ecx.expr_addr_of(test.span, ecx.expr_path(ecx.path(test.span, vec![test.ident])))
 353             })
 354             .collect(),
 355     )
 356 }
 357
 358 fn is_test_case(sess: &Session, i: &ast::Item) -> bool {
 359     sess.contains_name(&i.attrs, sym::rustc_test_marker)
 360 }
 361
 362 fn get_test_runner(
 363     sess: &Session,
 364     sd: &rustc_errors::Handler,
 365     krate: &ast::Crate,
 366 ) -> Option<ast::Path> {
 367     let test_attr = sess.find_by_name(&krate.attrs, sym::test_runner)?;
 368     let meta_list = test_attr.meta_item_list()?;
 369     let span = test_attr.span;
 370     match &*meta_list {
 371         [single] => match single.meta_item() {
 372             Some(meta_item) if meta_item.is_word() => return Some(meta_item.path.clone()),
 373             _ => sd.struct_span_err(span, "`test_runner` argument must be a path").emit(),
 374         },
 375         _ => sd.struct_span_err(span, "`#![test_runner(..)]` accepts exactly 1 argument").emit(),
 376     }
 377     None
 378 }