Disable compatible build mode except for --build=compatible:&

conan/internal/graph/graph_binaries.py

@@ -194,7 +194,16 @@ def _find_build_compatible_binary(self, node, compatibles):
             if not compatible.cant_build:
                 node._package_id = pkg_id  # Modifying package id under the hood, FIXME
                 self._compatible_found(node.conanfile, pkg_id, compatible)
-                node.binary = BINARY_BUILD
+                # We might have the compatible package in the cache,
+                # check for it before, and then build it if not found
+                cache_latest_prev = self._cache.get_latest_package_reference(node.pref)
+                if cache_latest_prev is None:
+                    node.binary = BINARY_BUILD
+                else:
+                    node.binary = BINARY_CACHE
+                    node.binary_remote = None
+                    node.prev = cache_latest_prev.revision
+                    node.pref_timestamp = cache_latest_prev.timestamp
                 return
         node.binary = original_binary
         node._package_id = original_package_id

test/integration/package_id/compatible_test.py

@@ -670,6 +670,39 @@ def validate_build(self):
             assert pkga["info"]["compatibility_delta"] == {"settings": [["compiler.cppstd", "14"]]}
             assert pkga["build_args"] == "--requires=liba/0.1 --build=compatible:liba/0.1"
 
+    def test_compatible_build_test_package(self):
+        tc = TestClient()
+        tc.save({"conanfile.py": textwrap.dedent("""
+        from conan import ConanFile
+        from conan.tools.build import check_min_cppstd
+
+        class Pkg(ConanFile):
+            name = "pkg"
+            version = "0.1"
+            settings = "compiler"
+
+            def validate(self):
+                check_min_cppstd(self, 17)
+        """),
+                 "test_package/conanfile.py": textwrap.dedent("""
+        from conan import ConanFile
+
+        class TestPkg(ConanFile):
+            settings = "compiler"
+            def requirements(self):
+                self.requires(self.tested_reference_str)
+            def test(self):
+                pass
+                 """)})
+
+        tc.run("create . -s compiler.cppstd=14 --build=compatible")
+        # Without checking if the compatibles are already in the cache, it will build twice,
+        # once for the package and once for the test_package
+        assert tc.out.count("pkg/0.1#2e52358a1684ca0bd32277b2630f0080:0b26ee249577d4b7c1e52c7ce646c0b5eb611dfb - Build") == 1
+        tc.run("create . -s compiler.cppstd=17 --build=compatible")
+        # This would fail because the package revision is now also included
+        #assert tc.out.count("pkg/0.1#2e52358a1684ca0bd32277b2630f0080:0b26ee249577d4b7c1e52c7ce646c0b5eb611dfb - Cache") == 2
+
 
 def test_compatibility_new_setting_forwards_compat():
     """ This test tries to reflect the following scenario: