fixes #559

Author: jph00

fastcore/_modidx.py

@@ -612,6 +612,7 @@
                                 'fastcore.xtras.autostart': ('xtras.html#autostart', 'fastcore/xtras.py'),
                                 'fastcore.xtras.bunzip': ('xtras.html#bunzip', 'fastcore/xtras.py'),
                                 'fastcore.xtras.console_help': ('xtras.html#console_help', 'fastcore/xtras.py'),
+                                'fastcore.xtras.dataclass_src': ('xtras.html#dataclass_src', 'fastcore/xtras.py'),
                                 'fastcore.xtras.dict2obj': ('xtras.html#dict2obj', 'fastcore/xtras.py'),
                                 'fastcore.xtras.dumps': ('xtras.html#dumps', 'fastcore/xtras.py'),
                                 'fastcore.xtras.get_source_link': ('xtras.html#get_source_link', 'fastcore/xtras.py'),
@@ -643,6 +644,7 @@
                                 'fastcore.xtras.stringfmt_names': ('xtras.html#stringfmt_names', 'fastcore/xtras.py'),
                                 'fastcore.xtras.trace': ('xtras.html#trace', 'fastcore/xtras.py'),
                                 'fastcore.xtras.truncstr': ('xtras.html#truncstr', 'fastcore/xtras.py'),
+                                'fastcore.xtras.type2str': ('xtras.html#type2str', 'fastcore/xtras.py'),
                                 'fastcore.xtras.untar_dir': ('xtras.html#untar_dir', 'fastcore/xtras.py'),
                                 'fastcore.xtras.utc2local': ('xtras.html#utc2local', 'fastcore/xtras.py'),
                                 'fastcore.xtras.walk': ('xtras.html#walk', 'fastcore/xtras.py')}}}

fastcore/xtras.py

@@ -9,7 +9,7 @@
            'repr_dict', 'is_listy', 'mapped', 'IterLen', 'ReindexCollection', 'get_source_link', 'truncstr',
            'sparkline', 'modify_exception', 'round_multiple', 'set_num_threads', 'join_path_file', 'autostart',
            'EventTimer', 'stringfmt_names', 'PartialFormatter', 'partial_format', 'utc2local', 'local2utc', 'trace',
-           'modified_env', 'ContextManagers', 'shufflish', 'console_help', 'hl_md']
+           'modified_env', 'ContextManagers', 'shufflish', 'console_help', 'hl_md', 'type2str', 'dataclass_src']
 
 # %% ../nbs/03_xtras.ipynb 2
 from .imports import *
@@ -576,3 +576,23 @@ def hl_md(s, lang='xml', show=True):
         from IPython import display
         return display.Markdown(md)
     except ImportError: print(s)
+
+# %% ../nbs/03_xtras.ipynb 162
+def type2str(typ:type)->str:
+    "Stringify `typ`"
+    if typ is None or typ is NoneType: return 'None'
+    if hasattr(typ, '__origin__'):
+        args = ", ".join(type2str(arg) for arg in typ.__args__)
+        if typ.__origin__ is Union: return f"Union[{args}]"
+        return f"{typ.__origin__.__name__}[{args}]"
+    elif isinstance(typ, type): return typ.__name__
+    return str(typ)
+
+# %% ../nbs/03_xtras.ipynb 164
+def dataclass_src(cls):
+    import dataclasses
+    src = f"@dataclass\nclass {cls.__name__}:\n"
+    for f in dataclasses.fields(cls):
+        d = "" if f.default is dataclasses.MISSING else f" = {f.default!r}"
+        src += f"    {f.name}: {type2str(f.type)}{d}\n"
+    return src

nbs/03_xtras.ipynb

@@ -2407,6 +2407,81 @@
     "hl_md('<test><xml foo=\"bar\">a child</xml></test>')"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#| export\n",
+    "def type2str(typ:type)->str:\n",
+    "    \"Stringify `typ`\"\n",
+    "    if typ is None or typ is NoneType: return 'None'\n",
+    "    if hasattr(typ, '__origin__'):\n",
+    "        args = \", \".join(type2str(arg) for arg in typ.__args__)\n",
+    "        if typ.__origin__ is Union: return f\"Union[{args}]\"\n",
+    "        return f\"{typ.__origin__.__name__}[{args}]\"\n",
+    "    elif isinstance(typ, type): return typ.__name__\n",
+    "    return str(typ)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "test_eq(type2str(Optional[float]), 'Union[float, None]')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#| export\n",
+    "def dataclass_src(cls):\n",
+    "    import dataclasses\n",
+    "    src = f\"@dataclass\\nclass {cls.__name__}:\\n\"\n",
+    "    for f in dataclasses.fields(cls):\n",
+    "        d = \"\" if f.default is dataclasses.MISSING else f\" = {f.default!r}\"\n",
+    "        src += f\"    {f.name}: {type2str(f.type)}{d}\\n\"\n",
+    "    return src"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from dataclasses import make_dataclass, dataclass"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "@dataclass\n",
+      "class DC:\n",
+      "    x: int\n",
+      "    y: Union[float, None] = None\n",
+      "    z: float = None\n",
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "DC = make_dataclass('DC', [('x', int), ('y', Optional[float], None), ('z', float, None)])\n",
+    "print(dataclass_src(DC))"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},