allow conan run [tool_requires]

conan/api/subapi/graph.py

@@ -87,8 +87,6 @@ def load_root_test_conanfile(self, path, tested_reference, profile_host, profile
     def _load_root_virtual_conanfile(self, profile_host, profile_build, requires, tool_requires,
                                      lockfile, remotes, update, check_updates=False,
                                      python_requires=None):
-        if not python_requires and not requires and not tool_requires:
-            raise ConanException("Provide requires or tool_requires")
         loader = self._helpers.loader
         conanfile = loader.load_virtual(requires=requires,
                                         tool_requires=tool_requires,

conan/cli/commands/run.py

@@ -34,6 +34,14 @@ def run(conan_api, parser, *args):
         # Default values for install
         setattr(args, "output_folder", tmpdir)
         setattr(args, "generator", [])
+        # If there is no conanfile in the cwd and no --requires/--tool-requires,
+        # use an in-memory virtual conanfile so that a profile [tool_requires]
+        # section is enough and executables from them can be executed
+        if args.path == "." and not args.requires and not args.tool_requires \
+                and not os.path.isfile(os.path.join(cwd, "conanfile.py")) \
+                and not os.path.isfile(os.path.join(cwd, "conanfile.txt")):
+            args.path = None
+            args.tool_requires = []
         try:
             deps_graph, lockfile, _ = _run_install_command(conan_api, args, cwd,
                                                            return_install_error=False)

test/integration/command/test_run.py

@@ -103,3 +103,36 @@ def test_run_status_is_propagated(client):
     client.run("run false --requires=pkg/0.1", assert_error=True)
     assert "Error installing the dependencies" not in client.out
     assert "ERROR: Error 1 while executing" in client.out
+
+
+def test_run_no_conanfile_profile_tool_requires():
+    # https://github.com/conan-io/conan/issues/20206
+    # When no conanfile exists in cwd and no --requires/--tool-requires is
+    # given, a profile [tool_requires] alone should be enough to drive the
+    # graph. Previously this failed with "Conanfile not found".
+    tc = TestClient()
+    conanfile = textwrap.dedent("""
+        from conan import ConanFile
+        from conan.tools.files import save
+        import os
+
+        class Pkg(ConanFile):
+            name = "pkg"
+            version = "0.1"
+            package_type = "application"
+
+            def package(self):
+                exe = os.path.join(self.package_folder, "bin", '""" + executable + """')
+                save(self, exe, "echo Hello World!")
+                os.chmod(exe, 0o755)
+        """)
+    tc.save({"pkg/conanfile.py": conanfile})
+    tc.run("create pkg")
+    profile = textwrap.dedent("""
+        include(default)
+        [tool_requires]
+        pkg/0.1
+        """)
+    tc.save({"myprofile": profile}, clean_first=True)
+    tc.run(f"run {executable} -pr:h=myprofile")
+    assert "Hello World!" in tc.out