Improve custom code extension

- Uses `gr.Code` component
- Includes example
- Can return out of body

scripts/custom_code.py

 import modules.scripts as scripts
 import gradio as gr
+import ast
+import copy
 
 from modules.processing import Processed
 from modules.shared import opts, cmd_opts, state
 
+
+def convertExpr2Expression(expr):
+    expr.lineno = 0
+    expr.col_offset = 0
+    result = ast.Expression(expr.value, lineno=0, col_offset = 0)
+
+    return result
+
+
+def exec_with_return(code, module):
+    """
+    like exec() but can return values
+    https://stackoverflow.com/a/52361938/5862977
+    """
+    code_ast = ast.parse(code)
+
+    init_ast = copy.deepcopy(code_ast)
+    init_ast.body = code_ast.body[:-1]
+
+    last_ast = copy.deepcopy(code_ast)
+    last_ast.body = code_ast.body[-1:]
+
+    exec(compile(init_ast, "<ast>", "exec"), module.__dict__)
+    if type(last_ast.body[0]) == ast.Expr:
+        return eval(compile(convertExpr2Expression(last_ast.body[0]), "<ast>", "eval"), module.__dict__)
+    else:
+        exec(compile(last_ast, "<ast>", "exec"), module.__dict__)
+
+
 class Script(scripts.Script):
 
     def title(self):
@@ -13,12 +44,23 @@ class Script(scripts.Script):
         return cmd_opts.allow_code
 
     def ui(self, is_img2img):
-        code = gr.Textbox(label="Python code", lines=1, elem_id=self.elem_id("code"))
+        example = """from modules.processing import process_images
+
+p.width = 768
+p.height = 768
+p.batch_size = 2
+p.steps = 10
+
+return process_images(p)
+"""
+
 
-        return [code]
+        code = gr.Code(value=example, language="python", label="Python code", elem_id=self.elem_id("code"))
+        indent_level = gr.Number(label='Indent level', value=2, precision=0, elem_id=self.elem_id("indent_level"))
 
+        return [code, indent_level]
 
-    def run(self, p, code):
+    def run(self, p, code, indent_level):
         assert cmd_opts.allow_code, '--allow-code option must be enabled'
 
         display_result_data = [[], -1, ""]
@@ -29,13 +71,20 @@ class Script(scripts.Script):
             display_result_data[2] = i
 
         from types import ModuleType
-        compiled = compile(code, '', 'exec')
         module = ModuleType("testmodule")
         module.__dict__.update(globals())
         module.p = p
         module.display = display
-        exec(compiled, module.__dict__)
 
-        return Processed(p, *display_result_data)
+        indent = " " * indent_level
+        indented = code.replace('\n', '\n' + indent)
+        body = f"""def __webuitemp__():
+{indent}{indented}
+__webuitemp__()"""
+
+        result = exec_with_return(body, module)
 
+        if isinstance(result, Processed):
+            return result
 
+        return Processed(p, *display_result_data)