From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Yuri Khan Newsgroups: gmane.emacs.help Subject: Re: Parse a field in JSON given a path to the field Date: Sat, 13 Nov 2021 21:08:28 +0700 Message-ID: References: <87r1bmpm8n.fsf@alshehhi.io> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="10520"; mail-complaints-to="usenet@ciao.gmane.io" Cc: help-gnu-emacs To: Husain Alshehhi Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Sat Nov 13 15:10:10 2021 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mltjN-0002W5-Sy for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 13 Nov 2021 15:10:09 +0100 Original-Received: from localhost ([::1]:35726 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mltjM-0006vO-V0 for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 13 Nov 2021 09:10:08 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:36634) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlti0-0005cQ-Do for help-gnu-emacs@gnu.org; Sat, 13 Nov 2021 09:08:49 -0500 Original-Received: from [2607:f8b0:4864:20::92b] (port=40622 helo=mail-ua1-x92b.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mlthy-0000sh-60 for help-gnu-emacs@gnu.org; Sat, 13 Nov 2021 09:08:44 -0500 Original-Received: by mail-ua1-x92b.google.com with SMTP id y5so6939358ual.7 for ; Sat, 13 Nov 2021 06:08:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=azEwL+kwTlEJsg4NDnUWCAyMHsNGitjVEX3CWHnLdLc=; b=EkfA7itpWpRU88EewOHeTtnhLrNVmUdBy4fjI6oBDt2ZOUBY+qBkvFDdz8fKQj4229 deJW87o3fSOYokaMCPP8aEaY84itsv9RhpK4kIWK3VNO+zENEiqU+6ZWspiBNFm29ROy ziJo8tVYBrGhSh6lSA9XXNlq0vO4zzyEHtjs95txFCUSxs20slOBbXHZPZWwsRUgLXoW 3Wi1839qR6amDH41cAlkX+n5fNKMBUxI/YjGd80k2uxeRSeHonn1O8P5QZN5bKtE0tOX nScJZQj0/vyvai81tTVlJDYA+nQrDcN/XR7v5af8STqNooRpB8kSIcBtb3uvXwnNOAnt CDgA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=azEwL+kwTlEJsg4NDnUWCAyMHsNGitjVEX3CWHnLdLc=; b=7m2c7uv793wCwcXamw6H2G/VHZeVbtksueJH3CTnJqfcdi8XW7VWcEnvVoWkrhENaS fcp8P6cYnaRvkUq67zFbO2Um7W5V6XbpiM/Zn3sgLxRLz7UAQPRIknHV1osUoLnvbxc0 U96znyCwnRPaWbaF2oz34U8Yxg8Cqg64wkC5zL8n03TulzRC455rNMjZijjFZMoIltft bSOCZCb08dspG5KzJVXTUo/V9A2EhihxHV6/vx7bD2RqMfzslurNBN9/XkUnNUKbF1nC KPz47pGR1hjhw465WjYuLCsXi4sYtDMXWbVFMwRNa8DjSfXfsm56QG5xkZoD8NHPTVwN toMg== X-Gm-Message-State: AOAM533BapbrkTrRL9hNH86VBUWe0hqTkDoQOuoyXfFRj8is6cxF+kM7 xK/rYxdJ0v3ujW5u3KHw7zo/cIprDQMFEXEfHi0bHdRfA4E= X-Google-Smtp-Source: ABdhPJyjx//n0OLNaS/3QkO6oQ7w1jz8wGY7nK8i1A2OdtKuCEPbyevfFhZYUSQ+K+lMSY+xb7C/Kwd4hJyHg6aVINE= X-Received: by 2002:ab0:224c:: with SMTP id z12mr35256873uan.41.1636812520216; Sat, 13 Nov 2021 06:08:40 -0800 (PST) In-Reply-To: <87r1bmpm8n.fsf@alshehhi.io> X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::92b (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::92b; envelope-from=yurivkhan@gmail.com; helo=mail-ua1-x92b.google.com X-Spam_score_int: -12 X-Spam_score: -1.3 X-Spam_bar: - X-Spam_report: (-1.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:134570 Archived-At: On Fri, 12 Nov 2021 at 01:59, Husain Alshehhi wrote: > > Does emacs provide a function that can return a path from a JSON object? = I find something like this useful if I want a field from a nested, large JS= ON. I happen to have a limited implementation of JSON Pointer (RFC 6901). The limitation is that it assumes a JSON representation produced by: (let ((json-object-type 'alist) (json-array-type 'vector) (json-key-type 'string) (json-null :json-null)) (json-read-from-string "=E2=80=A6")) because at the time of writing I found that the most unambiguous representation offered: * distinguishes arrays from objects * distinguishes null, false, empty array, and empty object * preserves object property order (If someone wants to turn this into a proper package, please be my guest. A useful addition would be for =E2=80=98jsonpointer-eval=E2=80=99 to= support hash representation for JSON objects; this has better performance at the expense of losing property order and value readability.) ``` (require 'ert) (require 'seq) (eval-when-compile (require 'pcase) (require 'rx) (require 'subr-x)) (defun jsonpointer--unescape-tilde (token) "Unescape =E2=80=98~0=E2=80=99 to =E2=80=98~=E2=80=99 and =E2=80=98~1=E2= =80=99 to =E2=80=98/=E2=80=99 in TOKEN." (thread-last token (replace-regexp-in-string "~1" "/") (replace-regexp-in-string "~0" "~"))) (ert-deftest jsonpointer--unescape-tilde/test-slash () (should (equal (jsonpointer--unescape-tilde "foo~10") "foo/0"))) (ert-deftest jsonpointer--unescape-tilde/test-tilde () (should (equal (jsonpointer--unescape-tilde "foo~01") "foo~1"))) (ert-deftest jsonpointer--unescape-tilde/test-multiple () (should (equal (jsonpointer--unescape-tilde "foo~01~10~00~11") "foo~1/0~0/1"))) (defun jsonpointer-parse (string) "Parse a JSON Pointer from string representation STRING. Return a list of reference tokens with =E2=80=98~0=E2=80=99 and =E2=80=98~1= =E2=80=99 sequences unescaped. See RFC 6901 =C2=A7=C2=A7 3, 5." (when (not (string-empty-p string)) (assert (string-prefix-p "/" string)) (seq-map #'jsonpointer--unescape-tilde (cdr (split-string string "/"))))) (ert-deftest jsonpointer-parse/test-empty-pointer () (should (equal (jsonpointer-parse "") '()))) (ert-deftest jsonpointer-parse/test-empty-token () (should (equal (jsonpointer-parse "/") '("")))) (ert-deftest jsonpointer-parse/test-unescaped () (should (equal (jsonpointer-parse "/unescaped") '("unescaped")))) (ert-deftest jsonpointer-parse/test-tilde () (should (equal (jsonpointer-parse "/escaped~01") '("escaped~1")))) (ert-deftest jsonpointer-parse/test-slash () (should (equal (jsonpointer-parse "/escaped~10") '("escaped/0")))) (ert-deftest jsonpointer-parse/test-multiple () (should (equal (jsonpointer-parse "/mix~01/match~10/unescaped") '("mix~1" "match/0" "unescaped")))) (defun jsonpointer-eval (pointer json) "Evaluate a JSON Pointer against a JSON document. POINTER should be a list of reference tokens as parsed by =E2=80=98jsonpointer-parse=E2=80=99. See RFC 6901 =C2=A7 4. If at any point the token cannot be followed, signal an error." (seq-reduce (lambda (json token) (pcase `(,json ,token) (`(,(and (pred listp) (app (assoc token) `(,_ . ,item))) ,_) item) (`(,(pred vectorp) ,(and (rx bos (or "0" (seq (any "1-9") (* (any "0-9")))) eos) (app string-to-number (and (pred (<=3D 0)) (pred (> (length json))) index)))= ) (aref json index)) (_ (error "Cannot follow JSON pointer: %s token: %s json: %s" pointer token json)))) pointer json)) (defconst jsonpointer--eval-test-json '(("foo" . ["bar" "baz"]) ("" . 0) ("a/b" . 1) ("c%d" . 2) ("e^f" . 3) ("g|h" . 4) ("i\\j" . 5) ("k\"l" . 6) (" " . 7) ("m~n" . 8))) (ert-deftest jsonpointer-eval/test-empty-pointer () (should (equal (jsonpointer-eval '() jsonpointer--eval-test-json) jsonpointer--eval-test-json))) (ert-deftest jsonpointer-eval/test-unescaped () (should (equal (jsonpointer-eval '("foo") jsonpointer--eval-test-json) ["bar" "baz"]))) (ert-deftest jsonpointer-eval/test-multi-token () (should (equal (jsonpointer-eval '("foo" "0") jsonpointer--eval-test-json) "bar"))) (ert-deftest jsonpointer-eval/test-empty-token () (should (equal (jsonpointer-eval '("") jsonpointer--eval-test-json) 0))) (ert-deftest jsonpointer-eval/test-slash () (should (equal (jsonpointer-eval '("a/b") jsonpointer--eval-test-json) 1))) (ert-deftest jsonpointer-eval/test-percent () (should (equal (jsonpointer-eval '("c%d") jsonpointer--eval-test-json) 2))) (ert-deftest jsonpointer-eval/test-caret () (should (equal (jsonpointer-eval '("e^f") jsonpointer--eval-test-json) 3))) (ert-deftest jsonpointer-eval/test-pipe () (should (equal (jsonpointer-eval '("g|h") jsonpointer--eval-test-json) 4))) (ert-deftest jsonpointer-eval/test-backslash () (should (equal (jsonpointer-eval '("i\\j") jsonpointer--eval-test-json) 5))) (ert-deftest jsonpointer-eval/test-quote () (should (equal (jsonpointer-eval '("k\"l") jsonpointer--eval-test-json) 6))) (ert-deftest jsonpointer-eval/test-space () (should (equal (jsonpointer-eval '(" ") jsonpointer--eval-test-json) 7))) (ert-deftest jsonpointer-eval/test-tilde () (should (equal (jsonpointer-eval '("m~n") jsonpointer--eval-test-json) 8))) (provide 'jsonpointer) ```