fix upload_policy=skip --build=missing issues (#15336)

* fix upload_policy=skip --build=missing issues

* review

conans/client/graph/graph_binaries.py

@@ -206,12 +206,11 @@ def _process_node(self, node, build_mode, remotes, update):
                 break
 
         if node.conanfile.upload_policy == "skip":
+            # Download/update shouldn't be checked in the servers if this is "skip-upload"
+            # The binary can only be in cache or missing.
             if cache_latest_prev:
                 node.binary = BINARY_CACHE
                 node.prev = cache_latest_prev.revision
-            elif build_mode.allowed(node.conanfile):
-                node.should_build = True
-                node.binary = BINARY_BUILD
             else:
                 node.binary = BINARY_MISSING
         elif cache_latest_prev is None:  # This binary does NOT exist in the cache

conans/test/integration/command/install/install_test.py

@@ -1,5 +1,6 @@
 import json
 import os
+import re
 import textwrap
 from collections import OrderedDict
 
@@ -488,6 +489,51 @@ def test_upload_skip_binaries_not_hit_server():
     assert "pkg/0.1: Created package" in c.out
 
 
+def test_upload_skip_build_missing():
+    c = TestClient(default_server_user=True)
+    pkg1 = GenConanfile("pkg1", "1.0").with_class_attribute('upload_policy = "skip"')
+    pkg2 = GenConanfile("pkg2", "1.0").with_requirement("pkg1/1.0", visible=False)
+    pkg3 = GenConanfile("pkg3", "1.0").with_requirement("pkg2/1.0")
+    c.save({"pkg1/conanfile.py": pkg1,
+            "pkg2/conanfile.py": pkg2,
+            "pkg3/conanfile.py": pkg3,
+            })
+    c.run("create pkg1")
+    c.run("create pkg2")
+    c.run("remove pkg1/*:* -c")  # remove binaries
+    c.run("create pkg3 --build=missing")
+    assert re.search(r"Skipped binaries(\s*)pkg1/1.0", c.out)
+
+
+def test_upload_skip_build_compatibles():
+    c = TestClient()
+    pkg1 = textwrap.dedent("""\
+        from conan import ConanFile
+        class Pkg1(ConanFile):
+            name = "pkg1"
+            version = "1.0"
+            settings = "build_type"
+            upload_policy = "skip"
+            def compatibility(self):
+                if self.settings.build_type == "Debug":
+                    return [{"settings": [("build_type", "Release")]}]
+            """)
+    pkg2 = GenConanfile("pkg2", "1.0").with_requirement("pkg1/1.0")
+    pkg3 = GenConanfile("pkg3", "1.0").with_requirement("pkg2/1.0")
+    c.save({"pkg1/conanfile.py": pkg1,
+            "pkg2/conanfile.py": pkg2,
+            "pkg3/conanfile.py": pkg3,
+            })
+    c.run("create pkg1 -s build_type=Release")
+    pkg1id = c.created_package_id("pkg1/1.0")
+    c.run("create pkg2 -s build_type=Release")
+    c.run("remove pkg1/*:* -c")  # remove binaries
+    c.run("create pkg3 -s build_type=Release --build=missing")
+    c.assert_listed_binary({"pkg1/1.0": (pkg1id, "Build")})
+    c.run("install pkg3 -s build_type=Debug --build=missing")
+    c.assert_listed_binary({"pkg1/1.0": (pkg1id, "Cache")})
+
+
 def test_install_json_format():
     # https://github.com/conan-io/conan/issues/14414
     client = TestClient()