define install_folder to be usable by custom generators

conans/client/manager.py

@@ -20,6 +20,7 @@ def deps_install(app, ref_or_path, install_folder, graph_info, remotes=None, bui
                  manifest_interactive=False, generators=None, no_imports=False,
                  create_reference=None, keep_build=False, use_lock=False, recorder=None):
     """ Fetch and build all dependencies for the given reference
+    :param app: The ConanApp instance with all collaborators
     @param ref_or_path: ConanFileReference or path to user space conanfile
     @param install_folder: where the output files will be saved
     @param build_modes: List of build_modes specified
@@ -31,6 +32,7 @@ def deps_install(app, ref_or_path, install_folder, graph_info, remotes=None, bui
     @param generators: List of generators from command line. If False, no generator will be
     written
     @param no_imports: Install specified packages but avoid running imports
+
     """
     out, user_io, graph_manager, cache = app.out, app.user_io, app.graph_manager, app.cache
     remote_manager, hook_manager = app.remote_manager, app.hook_manager
@@ -77,6 +79,7 @@ def deps_install(app, ref_or_path, install_folder, graph_info, remotes=None, bui
         manifest_manager.print_log()
 
     if install_folder:
+        conanfile.install_folder = install_folder
         # Write generators
         output = conanfile.output if conanfile.display_name != "virtual" else out
         if generators is not False:

conans/test/functional/generators/custom_generator_test.py

@@ -1,4 +1,5 @@
 import os
+import textwrap
 import unittest
 
 from conans.model.ref import ConanFileReference
@@ -147,3 +148,27 @@ class MyCustomGeneratorWithTemplatePackage(ConanFile):
         client.run("install gen/0.1@user/stable -g=MyCustomTemplateGenerator")
         generated = load(os.path.join(client.current_folder, "customfile.gen"))
         self.assertEqual(generated, "Template: Hello")
+
+    def install_folder_test(self):
+        # https://github.com/conan-io/conan/issues/5568
+        templated_generator = textwrap.dedent("""
+            from conans import ConanFile
+            from conans.model import Generator
+            class MyGenerator(Generator):
+                @property
+                def filename(self):
+                    return "customfile.gen"
+                @property
+                def content(self):
+                    return self.conanfile.install_folder
+
+            class MyCustomGenerator(ConanFile):
+                pass
+            """)
+        client = TestClient()
+        client.save({CONANFILE: templated_generator, "mytemplate.txt": "Template: %s"})
+        client.run("create . gen/0.1@user/stable")
+        client.run("install gen/0.1@user/stable -g=MyGenerator")
+        generated = load(os.path.join(client.current_folder, "customfile.gen"))
+        self.assertEqual(generated, client.current_folder)
+