fix error with lock install when lockfile uses a path (#14836)

conans/client/conan_api.py

@@ -1396,6 +1396,8 @@ def lock_install(self, lockfile, remote_name=None, build=None,
         graph_lock = graph_info.graph_lock
         root_id = graph_lock.root_node_id()
         reference = graph_lock.nodes[root_id].ref
+        if reference is None:
+            reference = graph_lock.nodes[root_id].path
         if recipes:
             graph = self.app.graph_manager.load_graph(reference, create_reference=None,
                                                       graph_info=graph_info, build_mode=None,

conans/test/functional/graph_lock/lock_install_test.py

@@ -48,3 +48,28 @@ def test_install_recipes():
     assert "pkga/0.1@user/channel:5ab84d6acfe1f23c4fae0ab88f26e3a396351ac9 - Download" in client.out
     assert "pkgb/0.1@user/channel:cfd10f60aeaa00f5ca1f90b5fe97c3fe19e7ec23 - Download" in client.out
 
+
+def test_install_txt():
+    """ lock install from a lockfile created from a conanfile path needs that conanfile to be
+    in the place it was to create the lockfile, otherwise it fails. So not really a great
+    use case
+    """
+    client = TestClient()
+    client.save({"conanfile.py": GenConanfile("pkga", "0.1").with_package_file("file.h", "0.1")})
+    client.run("create . user/channel")
+
+    # Use a consumer with a version range
+    client.save({"conanfile.py":
+                 GenConanfile("pkgb", "0.1").with_require("pkga/[>=0.1]@user/channel")})
+    client.run("create . user/channel")
+    client.save({"conanfile.txt": "[requires]\npkgb/0.1@user/channel"}, clean_first=True)
+    client.run("lock create conanfile.txt --lockfile-out=lock1.lock")
+
+    # We can create a pkga/0.2, but it will not be used
+    client.save({"conanfile.py": GenConanfile("pkga", "0.2").with_package_file("file.h", "0.2")})
+    client.run("create . user/channel")
+
+    client.run("lock install lock1.lock -g deploy")
+    assert "pkga/0.1@user/channel from local cache" in client.out
+    file_h = client.load("pkga/file.h")
+    assert file_h == "0.1"