Extract logic of all test target filter to all_test_targets

src/bin/cargo/commands/test.rs

@@ -105,16 +105,12 @@ pub fn exec(config: &mut Config, args: &ArgMatches) -> CliResult {
             FilterRule::none(),
             FilterRule::none(),
         );
-    } else if test_name.is_some() {
-        if let CompileFilter::Default { .. } = compile_opts.filter {
-            compile_opts.filter = ops::CompileFilter::new(
-                LibRule::Default,   // compile the library, so the unit tests can be run filtered
-                FilterRule::none(), // binaries without `test = false` are included by default
-                FilterRule::All, // compile the tests, so the integration tests can be run filtered
-                FilterRule::none(), // specify --examples to unit test binaries filtered
-                FilterRule::none(), // specify --benches to unit test benchmarks filtered
-            ); // also, specify --doc to run doc tests filtered
-        }
+    } else if test_name.is_some() && !compile_opts.filter.is_specific() {
+        // If arg `TESTNAME` is provided, assumed that the user knows what
+        // exactly they wants to test, so we use `all_test_targets` to
+        // avoid compiling unnecessary targets such as examples, which are
+        // included by the logic of default target filter.
+        compile_opts.filter = ops::CompileFilter::all_test_targets();
     }
 
     let ops = ops::TestOptions {

src/cargo/ops/cargo_compile.rs

@@ -828,6 +828,25 @@ impl CompileFilter {
         }
     }
 
+    /// Constructs a filter that includes all test targets.
+    ///
+    /// Being different from the behavior of [`CompileFilter::Default`], this
+    /// function only recongnizes test targets, which means cargo might compile
+    /// all targets with `tested` flag on, whereas [`CompileFilter::Default`]
+    /// may include additional example targets to ensure they can be compiled.
+    ///
+    /// Note that the actual behavior is subject to `filter_default_targets`
+    /// and `generate_targets` though.
+    pub fn all_test_targets() -> Self {
+        Self::Only {
+            all_targets: false,
+            lib: LibRule::Default,
+            bins: FilterRule::none(),
+            examples: FilterRule::none(),
+            tests: FilterRule::All,
+            benches: FilterRule::none(),
+        }
+    }
     pub fn need_dev_deps(&self, mode: CompileMode) -> bool {
         match mode {
             CompileMode::Test | CompileMode::Doctest | CompileMode::Bench => true,