Blog post:
https://nim-lang.org/blog/2021/10/19/version-160-released.html

Changelog:
https://github.com/nim-lang/Nim/blob/version-1-6/changelogs/changelog_1_6_0.md

This commit pulls in the latest changes to the json module from the Nim
standard library.

The `json.nim` file in the configlet repo is the result of applying the
below patch to the upstream 1.6.0 `json.nim` file.

diff --git a/Nim/lib/pure/json.nim b/configlet/src/patched_stdlib/json.nim
index 85c3393..55daa6d 100644
--- a/Nim/lib/pure/json.nim
+++ b/configlet/src/patched_stdlib/json.nim
@@ -1,11 +1,28 @@
-#
-#
-#            Nim's Runtime Library
-#        (c) Copyright 2015 Andreas Rumpf, Dominik Picheta
-#
-#    See the file "copying.txt", included in this
-#    distribution, for details about the copyright.
-#
+# This file is minimally adapted from this version in the Nim standard library:
+# https://github.com/nim-lang/Nim/blob/58080525a1dc/lib/pure/json.nim
+# The standard library version is lenient: it silently allows a trailing comma.
+# The below version is stricter: it raises a `JsonParsingError` for a trailing
+# comma.
+
+# Copyright (c) 2015 Andreas Rumpf, Dominik Picheta
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.

 ## This module implements a simple high performance `JSON`:idx:
 ## parser. JSON (JavaScript Object Notation) is a lightweight
@@ -893,6 +910,9 @@ proc parseJson(p: var JsonParser; rawIntegers, rawFloats: bool): JsonNode =
       result[key] = val
       if p.tok != tkComma: break
       discard getTok(p)
+      # Raise `JsonParsingError` for a trailing comma, unlike `std/json`
+      if p.tok == tkCurlyRi:
+        raiseParseErr(p, "found trailing comma. } or key/value pair")
     eat(p, tkCurlyRi)
   of tkBracketLe:
     result = newJArray()
@@ -901,6 +921,9 @@ proc parseJson(p: var JsonParser; rawIntegers, rawFloats: bool): JsonNode =
       result.add(parseJson(p, rawIntegers, rawFloats))
       if p.tok != tkComma: break
       discard getTok(p)
+      # Raise `JsonParsingError` for a trailing comma, unlike `std/json`
+      if p.tok == tkBracketRi:
+        raiseParseErr(p, "found trailing comma. ] or array item")
     eat(p, tkBracketRi)
   of tkError, tkCurlyRi, tkBracketRi, tkColon, tkComma, tkEof:
     raiseParseErr(p, "{")

This commit pulls in the latest changes to the parsejson module from the
Nim standard library.

The `parsejson.nim` file in the configlet repo is the result of applying
the below patch to the upstream 1.6.0 `parsejson.nim` file.

diff --git a/Nim/lib/pure/parsejson.nim b/configlet/src/patched_stdlib/parsejson.nim
index 196d8c3..48e1e05 100644
--- a/Nim/lib/pure/parsejson.nim
+++ b/configlet/src/patched_stdlib/parsejson.nim
@@ -1,11 +1,29 @@
-#
-#
-#            Nim's Runtime Library
-#        (c) Copyright 2018 Nim contributors
-#
-#    See the file "copying.txt", included in this
-#    distribution, for details about the copyright.
-#
+# This file is minimally adapted from this version in the Nim standard library:
+# https://github.com/nim-lang/Nim/blob/285539c87aa2/lib/pure/parsejson.nim
+# The standard library version is lenient: it silently allows line comments
+# with `//`, and long comments with `/* */`.
+# The below version is stricter: it raises a `JsonParsingError` for such
+# comments.
+
+# Copyright (c) 2018 Nim contributors
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.

 ## This module implements a json parser. It is used
 ## and exported by the `json` standard library
@@ -54,7 +72,6 @@ type
     errBracketRiExpected, ## `]` expected
     errCurlyRiExpected,   ## `}` expected
     errQuoteExpected,     ## `"` or `'` expected
-    errEOC_Expected,      ## `*/` expected
     errEofExpected,       ## EOF expected
     errExprExpected       ## expr expected

@@ -85,7 +102,6 @@ const
     "']' expected",
     "'}' expected",
     "'\"' or \"'\" expected",
-    "'*/' expected",
     "EOF expected",
     "expression expected"
   ]
@@ -263,43 +279,8 @@ proc skip(my: var JsonParser) =
   var pos = my.bufpos
   while true:
     case my.buf[pos]
-    of '/':
-      if my.buf[pos+1] == '/':
-        # skip line comment:
-        inc(pos, 2)
-        while true:
-          case my.buf[pos]
-          of '\0':
-            break
-          of '\c':
-            pos = lexbase.handleCR(my, pos)
-            break
-          of '\L':
-            pos = lexbase.handleLF(my, pos)
-            break
-          else:
-            inc(pos)
-      elif my.buf[pos+1] == '*':
-        # skip long comment:
-        inc(pos, 2)
-        while true:
-          case my.buf[pos]
-          of '\0':
-            my.err = errEOC_Expected
-            break
-          of '\c':
-            pos = lexbase.handleCR(my, pos)
-          of '\L':
-            pos = lexbase.handleLF(my, pos)
-          of '*':
-            inc(pos)
-            if my.buf[pos] == '/':
-              inc(pos)
-              break
-          else:
-            inc(pos)
-      else:
-        break
+    # Raise `JsonParsingError` for comments with `//` or `/* */`,
+    # unlike `std/parsejson`
     of ' ', '\t':
       inc(pos)
     of '\c':
@@ -350,7 +331,7 @@ proc parseName(my: var JsonParser) =

 proc getTok*(my: var JsonParser): TokKind =
   setLen(my.a, 0)
-  skip(my) # skip whitespace, comments
+  skip(my) # skip whitespace
   case my.buf[my.bufpos]
   of '-', '.', '0'..'9':
     parseNumber(my)