Similar to native match pattern for tuple structs, make matches_pattern enforce exhaustive field checks for tuple structs by default, to be suppressed by explicit .. at the end of the pattern.

This change is not backward-compatible since it enforces field exhaustiveness by default in the absence of a trailing `..` in the pattern.

Fixes #447

PiperOrigin-RevId: 704273542

Author: marcianx

googletest/src/matchers/matches_pattern.rs

@@ -369,6 +369,66 @@ pub mod internal {
             }
         }
     }
+
+    /// A matcher that ensures that the passed-in function compiles with the
+    /// benefit of inference from the value being tested. The passed-in
+    /// matcher is what is actually invoked for matching.
+    ///
+    /// It forwards all description responsibilities to the passed-in matcher.
+    pub fn compile_assert_and_match<T, M>(
+        must_compile_function: fn(&T),
+        matcher: M,
+    ) -> CompileAssertAndMatch<T, M> {
+        CompileAssertAndMatch { must_compile_function, matcher }
+    }
+
+    #[derive(MatcherBase)]
+    #[doc(hidden)]
+    pub struct CompileAssertAndMatch<T, M> {
+        #[allow(dead_code)]
+        must_compile_function: fn(&T),
+        matcher: M,
+    }
+
+    impl<'a, T: Debug, M> Matcher<&'a T> for CompileAssertAndMatch<T, M>
+    where
+        M: Matcher<&'a T>,
+    {
+        fn matches(&self, actual: &'a T) -> crate::matcher::MatcherResult {
+            self.matcher.matches(actual)
+        }
+
+        fn describe(
+            &self,
+            matcher_result: crate::matcher::MatcherResult,
+        ) -> crate::description::Description {
+            self.matcher.describe(matcher_result)
+        }
+
+        fn explain_match(&self, actual: &'a T) -> crate::description::Description {
+            self.matcher.explain_match(actual)
+        }
+    }
+
+    impl<T: Debug + Copy, M> Matcher<T> for CompileAssertAndMatch<T, M>
+    where
+        M: Matcher<T>,
+    {
+        fn matches(&self, actual: T) -> crate::matcher::MatcherResult {
+            self.matcher.matches(actual)
+        }
+
+        fn describe(
+            &self,
+            matcher_result: crate::matcher::MatcherResult,
+        ) -> crate::description::Description {
+            self.matcher.describe(matcher_result)
+        }
+
+        fn explain_match(&self, actual: T) -> crate::description::Description {
+            self.matcher.explain_match(actual)
+        }
+    }
 }
 
 mod compile_fail_tests {
@@ -393,6 +453,15 @@ mod compile_fail_tests {
     /// ```
     fn _dot_dot_supported_only_at_end_of_struct_pattern() {}
 
+    /// ```compile_fail
+    /// use ::googletest::prelude::*;
+    /// #[derive(Debug)]
+    /// struct Foo(u32, u32);
+    /// let actual = Foo(1, 2);
+    /// verify_that!(actual, matches_pattern!(Foo(eq(&1), .., )));
+    /// ```
+    fn _dot_dot_supported_only_at_end_of_tuple_struct_pattern() {}
+
     /// ```compile_fail
     /// use ::googletest::prelude::*;
     /// #[derive(Debug)]
@@ -412,4 +481,13 @@ mod compile_fail_tests {
     /// verify_that!(actual, matches_pattern!(Foo::Bar { a: eq(&1) }));
     /// ```
     fn _unexhaustive_enum_struct_field_check_requires_dot_dot() {}
+
+    /// ```compile_fail
+    /// use ::googletest::prelude::*;
+    /// #[derive(Debug)]
+    /// struct Foo(u32, u32, u32);
+    /// let actual = Foo(1, 2, 3);
+    /// verify_that!(actual, matches_pattern!(Foo(eq(&1), eq(&2) )));
+    /// ```
+    fn _unexhaustive_tuple_struct_field_check_requires_dot_dot() {}
 }

googletest/src/matchers/mod.rs

@@ -113,7 +113,9 @@ pub mod __internal_unstable_do_not_depend_on_these {
     pub use super::elements_are_matcher::internal::ElementsAre;
     pub use super::field_matcher::internal::field_matcher;
     pub use super::is_matcher::is;
-    pub use super::matches_pattern::internal::{__googletest_macro_matches_pattern, pattern_only};
+    pub use super::matches_pattern::internal::{
+        __googletest_macro_matches_pattern, compile_assert_and_match, pattern_only,
+    };
     pub use super::pointwise_matcher::internal::PointwiseMatcher;
     pub use super::property_matcher::internal::{property_matcher, property_ref_matcher};
     pub use super::result_of_matcher::internal::{result_of, result_of_ref};

googletest/tests/matches_pattern_test.rs

@@ -150,6 +150,20 @@ fn matches_struct_containing_non_copy_field_binding_mode() -> Result<()> {
     verify_that!(actual, matches_pattern!(AStruct { a_string: eq("123") }))
 }
 
+#[test]
+fn matches_generic_struct_exhaustively() -> Result<()> {
+    #[allow(dead_code)]
+    #[derive(Debug)]
+    struct AStruct<T> {
+        a: T,
+        b: u32,
+    }
+    let actual = AStruct { a: 1, b: 3 };
+
+    verify_that!(actual, matches_pattern!(&AStruct { a: _, b: _ }))?;
+    verify_that!(actual, matches_pattern!(AStruct { a: _, b: _ }))
+}
+
 #[test]
 fn matches_struct_with_interleaved_underscore() -> Result<()> {
     #[derive(Debug)]
@@ -481,6 +495,28 @@ fn matches_tuple_struct_with_interleaved_underscore() -> Result<()> {
     verify_that!(actual, matches_pattern!(AStruct(eq(&1), _, eq(&3))))
 }
 
+#[test]
+fn matches_tuple_struct_non_exhaustive() -> Result<()> {
+    #[allow(dead_code)]
+    #[derive(Debug)]
+    struct AStruct(i32, u32);
+    let actual = AStruct(1, 3);
+
+    verify_that!(actual, matches_pattern!(&AStruct(_, ..)))?;
+    verify_that!(actual, matches_pattern!(AStruct(_, ..)))
+}
+
+#[test]
+fn matches_generic_tuple_struct_exhaustively() -> Result<()> {
+    #[allow(dead_code)]
+    #[derive(Debug)]
+    struct AStruct<T>(T, u32);
+    let actual = AStruct(1, 3);
+
+    verify_that!(actual, matches_pattern!(&AStruct(_, _)))?;
+    verify_that!(actual, matches_pattern!(AStruct(_, _)))
+}
+
 #[test]
 fn matches_enum_without_field() -> Result<()> {
     #[derive(Debug)]

googletest_macro/src/matches_pattern.rs

@@ -16,9 +16,7 @@ use proc_macro2::{Delimiter, Group, Ident, Span, TokenStream, TokenTree};
 use quote::quote;
 use syn::{
     parse::{Parse, ParseStream, Parser as _},
-    parse_macro_input,
-    punctuated::Punctuated,
-    Expr, ExprCall, Pat, Token,
+    parse_macro_input, Expr, ExprCall, Pat, Token,
 };
 
 /// This is an implementation detail of `googletest::matches_pattern!`. It
@@ -164,22 +162,46 @@ fn parse_tuple_pattern_args(
     struct_name: TokenStream,
     group_content: TokenStream,
 ) -> syn::Result<TokenStream> {
-    let parser = Punctuated::<MaybeTupleFieldPattern, Token![,]>::parse_terminated;
-    let fields = parser
-        .parse2(group_content)?
+    let (patterns, non_exhaustive) =
+        parse_list_terminated_pattern::<MaybeTupleFieldPattern>.parse2(group_content)?;
+    let field_count = patterns.len();
+    let field_patterns = patterns
         .into_iter()
         .enumerate()
         .filter_map(|(index, maybe_pattern)| maybe_pattern.0.map(|pattern| (index, pattern)))
         .map(|(index, TupleFieldPattern { ref_token, matcher })| {
             let index = syn::Index::from(index);
             quote! { googletest::matchers::field!(#struct_name.#index, #ref_token #matcher) }
         });
-    Ok(quote! {
+
+    let matcher = quote! {
         googletest::matchers::__internal_unstable_do_not_depend_on_these::is(
             stringify!(#struct_name),
-            all!( #(#fields),* )
+            all!( #(#field_patterns),* )
         )
-    })
+    };
+
+    // Do an exhaustiveness check only if the pattern doesn't end with `..`.
+    if non_exhaustive {
+        Ok(matcher)
+    } else {
+        let empty_fields = std::iter::repeat(quote! { _ }).take(field_count);
+        Ok(quote! {
+            googletest::matchers::__internal_unstable_do_not_depend_on_these::compile_assert_and_match(
+                |actual| {
+                    // Exhaustively check that all field names are specified.
+                    match actual {
+                        #struct_name ( #(#empty_fields),* ) => (),
+                        // The pattern below is unreachable if the type is a struct (as opposed to
+                        // an enum). Since the macro can't know which it is, we always include it
+                        // and just tell the compiler not to complain.
+                        #[allow(unreachable_patterns)]
+                        _ => {},
+                    }
+                },
+                #matcher)
+        })
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -257,6 +279,13 @@ fn parse_braced_pattern_args(
         })
         .collect();
 
+    let matcher = quote! {
+        googletest::matchers::__internal_unstable_do_not_depend_on_these::is(
+            stringify!(#struct_name),
+            all!(#(#field_patterns),* )
+        )
+    };
+
     // Do an exhaustiveness check only if the pattern doesn't end with `..` and has
     // any fields in the pattern. This latter part is required because
     // `matches_pattern!` also uses the brace notation for tuple structs when
@@ -268,36 +297,25 @@ fn parse_braced_pattern_args(
     // matches_pattern!(foo, Struct { bar(): eq(1) })
     // ```
     // and we can't emit an exhaustiveness check based on the `matches_pattern!`.
-    let maybe_assert_exhaustive = if non_exhaustive || field_names.is_empty() {
-        None
+    if non_exhaustive || field_names.is_empty() {
+        Ok(matcher)
     } else {
-        // Note that `struct_name` might be an enum variant (`Enum::Foo`), which is not
-        // a valid type. So we need to infer the type, produce an instance, and match on
-        // it. Fortunately, `[_; 0]` can be trivially initialized to `[]` and can
-        // produce an instance by indexing into it without failing compilation.
-        Some(quote! {
-            fn __matches_pattern_ensure_exhastive_match(i: usize) {
-                let val: [_; 0] = [];
-                let _ = match val[i] {
-                    #struct_name { #(#field_names: _),* } => (),
-                    // The pattern below is unreachable if the type is a struct (as opposed to an
-                    // enum). Since the macro can't know which it is, we always include it and just
-                    // tell the compiler not to complain.
-                    #[allow(unreachable_patterns)]
-                    _ => (),
-                };
-            }
+        Ok(quote! {
+            googletest::matchers::__internal_unstable_do_not_depend_on_these::compile_assert_and_match(
+                |actual| {
+                    // Exhaustively check that all field names are specified.
+                    match actual {
+                        #struct_name { #(#field_names: _),* } => {},
+                        // The pattern below is unreachable if the type is a struct (as opposed to
+                        // an enum). Since the macro can't know which it is, we always include it
+                        // and just tell the compiler not to complain.
+                        #[allow(unreachable_patterns)]
+                        _ => {},
+                    }
+                },
+                #matcher)
         })
-    };
-
-    Ok(quote! {
-        googletest::matchers::__internal_unstable_do_not_depend_on_these::is(
-            stringify!(#struct_name), {
-                #maybe_assert_exhaustive
-                all!( #(#field_patterns),* )
-            }
-        )
-    })
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////