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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Invalid signature message received from the LSP server","articleBody":"See https://github.com/ycm-core/YouCompleteMe/issues/4313, which is rooted in an invalid signature message received from the LSP server. \n\nQuoting the YCM developer's analysis:\n\n\u003e The following message is received from the LSP server:\n\u003e \n\u003e ```\n\u003e ben@BenMBP2021 ~ % cat j | jq\n\u003e {\n\u003e   \"jsonrpc\": \"2.0\",\n\u003e   \"id\": 131,\n\u003e   \"result\": {\n\u003e     \"signatures\": [\n\u003e       {\n\u003e         \"label\": \"ufunc()\",\n\u003e         \"documentation\": {\n\u003e           \"kind\": \"plaintext\",\n\u003e           \"value\": \"isnan(x, \\\\/, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature])\\\\n\\\\nTest element-wise for NaN and return result as a boolean array.\\\\n\\\\nParameters\\\\n----------\\\\nx : array_like\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0Input array.\\\\nout : ndarray, None, or tuple of ndarray and None, optional\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0A location into which the result is stored. If provided, it must have\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0a shape that the inputs broadcast to. If not provided or None,\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0a freshly-allocated array is returned. A tuple (possible only as a\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0keyword argument) must have length equal to the number of outputs.\\\\nwhere : array_like, optional\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0This condition is broadcast over the input. At locations where the\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0condition is True, the `out` array will be set to the ufunc result.\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0Elsewhere, the `out` array will retain its original value.\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0Note that if an uninitialized `out` array is created via the default\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0``out=None``, locations within it where the condition is False will\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0remain uninitialized.\\\\n**kwargs\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0For other keyword-only arguments, see the\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0:ref:`ufunc docs \u003cufuncs.kwargs\u003e`.\\\\n\\\\nReturns\\\\n-------\\\\ny : ndarray or bool\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0True where ``x`` is NaN, false otherwise.\\\\n\\\\u00a0\\\\u00a0\\\\u00a0\\\\u00a0This is a scalar if `x` is a scalar.\\\\n\\\\nSee Also\\\\n--------\\\\nisinf, isneginf, isposinf, isfinite, isnat\\\\n\\\\nNotes\\\\n-----\\\\nNumPy uses the IEEE Standard for Binary Floating-Point for Arithmetic\\\\n(IEEE 754). This means that Not a Number is not equivalent to infinity.\\\\n\\\\nExamples\\\\n--------\\\\n\u003e\u003e\u003e import numpy as np\\\\n\u003e\u003e\u003e np.isnan(np.nan)\\\\nTrue\\\\n\u003e\u003e\u003e np.isnan(np.inf)\\\\nFalse\\\\n\u003e\u003e\u003e np.isnan([np.log(-1.),1.,np.log(0)])\\\\narray([ True, False, False])\"\n\u003e         },\n\u003e         \"parameters\": [\n\u003e           {\n\u003e             \"label\": \"args\",\n\u003e             \"documentation\": {\n\u003e               \"kind\": \"plaintext\",\n\u003e               \"value\": \"\"\n\u003e             }\n\u003e           },\n\u003e           {\n\u003e             \"label\": \"kwargs\",\n\u003e             \"documentation\": {\n\u003e               \"kind\": \"plaintext\",\n\u003e               \"value\": \"\"\n\u003e             }\n\u003e           }\n\u003e         ]\n\u003e       }\n\u003e     ],\n\u003e     \"activeSignature\": 0,\n\u003e     \"activeParameter\": 0\n\u003e   }\n\u003e }\n\u003e ```\n\u003e \n\u003e this is _invalid_ according to to the specification.\n\u003e \n\u003e The [specification](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_signatureHelp) states that the `label` of each `parameter` must be substring of the `label` of the signature.\n\u003e \n\u003e The `signature` label of `ufunc()` is clearly incorrect and thus invalid.\n\u003e \u003cimg alt=\"Image\" width=\"710\" height=\"552\" src=\"https://private-user-images.githubusercontent.com/10584846/500155677-d9101b1e-dac1-4d9e-b865-db680b91bf6f.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.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.lusXXqJoUuUbcIf_TK5k4vjvPY-1_dndUiCYMBNg928\"\u003e\n\u003e \n\u003e Please raise this with the developer of the language server or use YCM's supported built-in Python support via Jedi. Or disable signature help of course.","author":{"url":"https://github.com/amosnier","@type":"Person","name":"amosnier"},"datePublished":"2025-10-11T16:06:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/678/python-lsp-server/issues/678"}