1 files changed, 390 insertions, 0 deletions
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
new file mode 100644
index 000000000..0ebe29df9
--- /dev/null
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -0,0 +1,390 @@
+// Code that generates a test runner to run all the tests in a crate
+
+use rustc_ast as ast;
+use rustc_ast::entry::EntryPointType;
+use rustc_ast::mut_visit::{ExpectOne, *};
+use rustc_ast::ptr::P;
+use rustc_ast::{attr, ModKind};
+use rustc_expand::base::{ExtCtxt, ResolverExpand};
+use rustc_expand::expand::{AstFragment, ExpansionConfig};
+use rustc_feature::Features;
+use rustc_session::Session;
+use rustc_span::hygiene::{AstPass, SyntaxContext, Transparency};
+use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::{Span, DUMMY_SP};
+use rustc_target::spec::PanicStrategy;
+use smallvec::{smallvec, SmallVec};
+use tracing::debug;
+
+use std::{iter, mem};
+
+struct Test {
+    span: Span,
+    ident: Ident,
+}
+
+struct TestCtxt<'a> {
+    ext_cx: ExtCtxt<'a>,
+    panic_strategy: PanicStrategy,
+    def_site: Span,
+    test_cases: Vec<Test>,
+    reexport_test_harness_main: Option<Symbol>,
+    test_runner: Option<ast::Path>,
+}
+
+// Traverse the crate, collecting all the test functions, eliding any
+// existing main functions, and synthesizing a main test harness
+pub fn inject(sess: &Session, resolver: &mut dyn ResolverExpand, krate: &mut ast::Crate) {
+    let span_diagnostic = sess.diagnostic();
+    let panic_strategy = sess.panic_strategy();
+    let platform_panic_strategy = sess.target.panic_strategy;
+
+    // Check for #![reexport_test_harness_main = "some_name"] which gives the
+    // main test function the name `some_name` without hygiene. This needs to be
+    // unconditional, so that the attribute is still marked as used in
+    // non-test builds.
+    let reexport_test_harness_main =
+        sess.first_attr_value_str_by_name(&krate.attrs, sym::reexport_test_harness_main);
+
+    // Do this here so that the test_runner crate attribute gets marked as used
+    // even in non-test builds
+    let test_runner = get_test_runner(sess, span_diagnostic, &krate);
+
+    if sess.opts.test {
+        let panic_strategy = match (panic_strategy, sess.opts.unstable_opts.panic_abort_tests) {
+            (PanicStrategy::Abort, true) => PanicStrategy::Abort,
+            (PanicStrategy::Abort, false) => {
+                if panic_strategy == platform_panic_strategy {
+                    // Silently allow compiling with panic=abort on these platforms,
+                    // but with old behavior (abort if a test fails).
+                } else {
+                    span_diagnostic.err(
+                        "building tests with panic=abort is not supported \
+                                         without `-Zpanic_abort_tests`",
+                    );
+                }
+                PanicStrategy::Unwind
+            }
+            (PanicStrategy::Unwind, _) => PanicStrategy::Unwind,
+        };
+        generate_test_harness(
+            sess,
+            resolver,
+            reexport_test_harness_main,
+            krate,
+            &sess.features_untracked(),
+            panic_strategy,
+            test_runner,
+        )
+    }
+}
+
+struct TestHarnessGenerator<'a> {
+    cx: TestCtxt<'a>,
+    tests: Vec<Test>,
+}
+
+impl TestHarnessGenerator<'_> {
+    fn add_test_cases(&mut self, node_id: ast::NodeId, span: Span, prev_tests: Vec<Test>) {
+        let mut tests = mem::replace(&mut self.tests, prev_tests);
+
+        if !tests.is_empty() {
+            // Create an identifier that will hygienically resolve the test
+            // case name, even in another module.
+            let expn_id = self.cx.ext_cx.resolver.expansion_for_ast_pass(
+                span,
+                AstPass::TestHarness,
+                &[],
+                Some(node_id),
+            );
+            for test in &mut tests {
+                // See the comment on `mk_main` for why we're using
+                // `apply_mark` directly.
+                test.ident.span =
+                    test.ident.span.apply_mark(expn_id.to_expn_id(), Transparency::Opaque);
+            }
+            self.cx.test_cases.extend(tests);
+        }
+    }
+}
+
+impl<'a> MutVisitor for TestHarnessGenerator<'a> {
+    fn visit_crate(&mut self, c: &mut ast::Crate) {
+        let prev_tests = mem::take(&mut self.tests);
+        noop_visit_crate(c, self);
+        self.add_test_cases(ast::CRATE_NODE_ID, c.spans.inner_span, prev_tests);
+
+        // Create a main function to run our tests
+        c.items.push(mk_main(&mut self.cx));
+    }
+
+    fn flat_map_item(&mut self, i: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
+        let mut item = i.into_inner();
+        if is_test_case(&self.cx.ext_cx.sess, &item) {
+            debug!("this is a test item");
+
+            let test = Test { span: item.span, ident: item.ident };
+            self.tests.push(test);
+        }
+
+        // We don't want to recurse into anything other than mods, since
+        // mods or tests inside of functions will break things
+        if let ast::ItemKind::Mod(_, ModKind::Loaded(.., ref spans)) = item.kind {
+            let ast::ModSpans { inner_span: span, inject_use_span: _ } = *spans;
+            let prev_tests = mem::take(&mut self.tests);
+            noop_visit_item_kind(&mut item.kind, self);
+            self.add_test_cases(item.id, span, prev_tests);
+        }
+        smallvec![P(item)]
+    }
+}
+
+// Beware, this is duplicated in librustc_passes/entry.rs (with
+// `rustc_hir::Item`), so make sure to keep them in sync.
+fn entry_point_type(sess: &Session, item: &ast::Item, depth: usize) -> EntryPointType {
+    match item.kind {
+        ast::ItemKind::Fn(..) => {
+            if sess.contains_name(&item.attrs, sym::start) {
+                EntryPointType::Start
+            } else if sess.contains_name(&item.attrs, sym::rustc_main) {
+                EntryPointType::RustcMainAttr
+            } else if item.ident.name == sym::main {
+                if depth == 0 {
+                    // This is a top-level function so can be 'main'
+                    EntryPointType::MainNamed
+                } else {
+                    EntryPointType::OtherMain
+                }
+            } else {
+                EntryPointType::None
+            }
+        }
+        _ => EntryPointType::None,
+    }
+}
+/// A folder used to remove any entry points (like fn main) because the harness
+/// generator will provide its own
+struct EntryPointCleaner<'a> {
+    // Current depth in the ast
+    sess: &'a Session,
+    depth: usize,
+    def_site: Span,
+}
+
+impl<'a> MutVisitor for EntryPointCleaner<'a> {
+    fn flat_map_item(&mut self, i: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
+        self.depth += 1;
+        let item = noop_flat_map_item(i, self).expect_one("noop did something");
+        self.depth -= 1;
+
+        // Remove any #[rustc_main] or #[start] from the AST so it doesn't
+        // clash with the one we're going to add, but mark it as
+        // #[allow(dead_code)] to avoid printing warnings.
+        let item = match entry_point_type(self.sess, &item, self.depth) {
+            EntryPointType::MainNamed | EntryPointType::RustcMainAttr | EntryPointType::Start => {
+                item.map(|ast::Item { id, ident, attrs, kind, vis, span, tokens }| {
+                    let allow_ident = Ident::new(sym::allow, self.def_site);
+                    let dc_nested =
+                        attr::mk_nested_word_item(Ident::new(sym::dead_code, self.def_site));
+                    let allow_dead_code_item = attr::mk_list_item(allow_ident, vec![dc_nested]);
+                    let allow_dead_code = attr::mk_attr_outer(allow_dead_code_item);
+                    let attrs = attrs
+                        .into_iter()
+                        .filter(|attr| {
+                            !attr.has_name(sym::rustc_main) && !attr.has_name(sym::start)
+                        })
+                        .chain(iter::once(allow_dead_code))
+                        .collect();
+
+                    ast::Item { id, ident, attrs, kind, vis, span, tokens }
+                })
+            }
+            EntryPointType::None | EntryPointType::OtherMain => item,
+        };
+
+        smallvec![item]
+    }
+}
+
+/// Crawl over the crate, inserting test reexports and the test main function
+fn generate_test_harness(
+    sess: &Session,
+    resolver: &mut dyn ResolverExpand,
+    reexport_test_harness_main: Option<Symbol>,
+    krate: &mut ast::Crate,
+    features: &Features,
+    panic_strategy: PanicStrategy,
+    test_runner: Option<ast::Path>,
+) {
+    let mut econfig = ExpansionConfig::default("test".to_string());
+    econfig.features = Some(features);
+
+    let ext_cx = ExtCtxt::new(sess, econfig, resolver, None);
+
+    let expn_id = ext_cx.resolver.expansion_for_ast_pass(
+        DUMMY_SP,
+        AstPass::TestHarness,
+        &[sym::test, sym::rustc_attrs],
+        None,
+    );
+    let def_site = DUMMY_SP.with_def_site_ctxt(expn_id.to_expn_id());
+
+    // Remove the entry points
+    let mut cleaner = EntryPointCleaner { sess, depth: 0, def_site };
+    cleaner.visit_crate(krate);
+
+    let cx = TestCtxt {
+        ext_cx,
+        panic_strategy,
+        def_site,
+        test_cases: Vec::new(),
+        reexport_test_harness_main,
+        test_runner,
+    };
+
+    TestHarnessGenerator { cx, tests: Vec::new() }.visit_crate(krate);
+}
+
+/// Creates a function item for use as the main function of a test build.
+/// This function will call the `test_runner` as specified by the crate attribute
+///
+/// By default this expands to
+///
+/// ```ignore UNSOLVED (I think I still need guidance for this one. Is it correct? Do we try to make it run? How do we nicely fill it out?)
+/// #[rustc_main]
+/// pub fn main() {
+///     extern crate test;
+///     test::test_main_static(&[
+///         &test_const1,
+///         &test_const2,
+///         &test_const3,
+///     ]);
+/// }
+/// ```
+///
+/// Most of the Ident have the usual def-site hygiene for the AST pass. The
+/// exception is the `test_const`s. These have a syntax context that has two
+/// opaque marks: one from the expansion of `test` or `test_case`, and one
+/// generated  in `TestHarnessGenerator::flat_map_item`. When resolving this
+/// identifier after failing to find a matching identifier in the root module
+/// we remove the outer mark, and try resolving at its def-site, which will
+/// then resolve to `test_const`.
+///
+/// The expansion here can be controlled by two attributes:
+///
+/// [`TestCtxt::reexport_test_harness_main`] provides a different name for the `main`
+/// function and [`TestCtxt::test_runner`] provides a path that replaces
+/// `test::test_main_static`.
+fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
+    let sp = cx.def_site;
+    let ecx = &cx.ext_cx;
+    let test_id = Ident::new(sym::test, sp);
+
+    let runner_name = match cx.panic_strategy {
+        PanicStrategy::Unwind => "test_main_static",
+        PanicStrategy::Abort => "test_main_static_abort",
+    };
+
+    // test::test_main_static(...)
+    let mut test_runner = cx
+        .test_runner
+        .clone()
+        .unwrap_or_else(|| ecx.path(sp, vec![test_id, Ident::from_str_and_span(runner_name, sp)]));
+
+    test_runner.span = sp;
+
+    let test_main_path_expr = ecx.expr_path(test_runner);
+    let call_test_main = ecx.expr_call(sp, test_main_path_expr, vec![mk_tests_slice(cx, sp)]);
+    let call_test_main = ecx.stmt_expr(call_test_main);
+
+    // extern crate test
+    let test_extern_stmt =
+        ecx.stmt_item(sp, ecx.item(sp, test_id, vec![], ast::ItemKind::ExternCrate(None)));
+
+    // #[rustc_main]
+    let main_meta = ecx.meta_word(sp, sym::rustc_main);
+    let main_attr = ecx.attribute(main_meta);
+
+    // pub fn main() { ... }
+    let main_ret_ty = ecx.ty(sp, ast::TyKind::Tup(vec![]));
+
+    // If no test runner is provided we need to import the test crate
+    let main_body = if cx.test_runner.is_none() {
+        ecx.block(sp, vec![test_extern_stmt, call_test_main])
+    } else {
+        ecx.block(sp, vec![call_test_main])
+    };
+
+    let decl = ecx.fn_decl(vec![], ast::FnRetTy::Ty(main_ret_ty));
+    let sig = ast::FnSig { decl, header: ast::FnHeader::default(), span: sp };
+    let defaultness = ast::Defaultness::Final;
+    let main = ast::ItemKind::Fn(Box::new(ast::Fn {
+        defaultness,
+        sig,
+        generics: ast::Generics::default(),
+        body: Some(main_body),
+    }));
+
+    // Honor the reexport_test_harness_main attribute
+    let main_id = match cx.reexport_test_harness_main {
+        Some(sym) => Ident::new(sym, sp.with_ctxt(SyntaxContext::root())),
+        None => Ident::new(sym::main, sp),
+    };
+
+    let main = P(ast::Item {
+        ident: main_id,
+        attrs: vec![main_attr],
+        id: ast::DUMMY_NODE_ID,
+        kind: main,
+        vis: ast::Visibility { span: sp, kind: ast::VisibilityKind::Public, tokens: None },
+        span: sp,
+        tokens: None,
+    });
+
+    // Integrate the new item into existing module structures.
+    let main = AstFragment::Items(smallvec![main]);
+    cx.ext_cx.monotonic_expander().fully_expand_fragment(main).make_items().pop().unwrap()
+}
+
+/// Creates a slice containing every test like so:
+/// &[&test1, &test2]
+fn mk_tests_slice(cx: &TestCtxt<'_>, sp: Span) -> P<ast::Expr> {
+    debug!("building test vector from {} tests", cx.test_cases.len());
+    let ecx = &cx.ext_cx;
+
+    ecx.expr_array_ref(
+        sp,
+        cx.test_cases
+            .iter()
+            .map(|test| {
+                ecx.expr_addr_of(test.span, ecx.expr_path(ecx.path(test.span, vec![test.ident])))
+            })
+            .collect(),
+    )
+}
+
+fn is_test_case(sess: &Session, i: &ast::Item) -> bool {
+    sess.contains_name(&i.attrs, sym::rustc_test_marker)
+}
+
+fn get_test_runner(
+    sess: &Session,
+    sd: &rustc_errors::Handler,
+    krate: &ast::Crate,
+) -> Option<ast::Path> {
+    let test_attr = sess.find_by_name(&krate.attrs, sym::test_runner)?;
+    let meta_list = test_attr.meta_item_list()?;
+    let span = test_attr.span;
+    match &*meta_list {
+        [single] => match single.meta_item() {
+            Some(meta_item) if meta_item.is_word() => return Some(meta_item.path.clone()),
+            _ => {
+                sd.struct_span_err(span, "`test_runner` argument must be a path").emit();
+            }
+        },
+        _ => {
+            sd.struct_span_err(span, "`#![test_runner(..)]` accepts exactly 1 argument").emit();
+        }
+    }
+    None
+}