json_view: pointer tokens that cannot be array indices create objects

editable_document::set() chose an array for a null parent whenever the
token consisted of digits, so "01" threw parse_error.106 and the empty
token threw, while basic_json::operator[](json_pointer) has created an
object for such tokens since #5358. This broke
unit-json_view_edit_values on develop. Use the same RFC 6901 array index
test as basic_json.

Also re-indent the unflatten test that the astyle check flagged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/json_view.hpp

@@ -1313,7 +1313,7 @@ class basic_json_document
     /// member is set (added if missing), an array element assigned, and "-"
     /// or the size of the array appends. A null parent becomes what
     /// basic_json's operator[](json_pointer) makes of it: an array for "-"
-    /// and for digits (padded with nulls up to the index), an object otherwise.
+    /// and for array indices (padded with nulls up to the index), an object otherwise.
     template<typename V>
     view_type set(const json_pointer& ptr, V&& value)
     {
@@ -1329,7 +1329,11 @@ class basic_json_document
             {
                 return push_back(parent, std::forward<V>(value));
             }
-            const bool digits = std::all_of(token.begin(), token.end(), [](const char c)
+            // (a token that cannot be an array index, such as "01" or "", names an
+            // object member, as in basic_json)
+            const bool digits = !token.empty()
+                                && (token.size() == 1 || token[0] != '0')
+                                && std::all_of(token.begin(), token.end(), [](const char c)
             {
                 return c >= '0' && c <= '9';
             });

single_include/nlohmann/json_view.hpp

@@ -9067,7 +9067,7 @@ class basic_json_document
     /// member is set (added if missing), an array element assigned, and "-"
     /// or the size of the array appends. A null parent becomes what
     /// basic_json's operator[](json_pointer) makes of it: an array for "-"
-    /// and for digits (padded with nulls up to the index), an object otherwise.
+    /// and for array indices (padded with nulls up to the index), an object otherwise.
     template<typename V>
     view_type set(const json_pointer& ptr, V&& value)
     {
@@ -9083,7 +9083,11 @@ class basic_json_document
             {
                 return push_back(parent, std::forward<V>(value));
             }
-            const bool digits = std::all_of(token.begin(), token.end(), [](const char c)
+            // (a token that cannot be an array index, such as "01" or "", names an
+            // object member, as in basic_json)
+            const bool digits = !token.empty()
+                                && (token.size() == 1 || token[0] != '0')
+                                && std::all_of(token.begin(), token.end(), [](const char c)
             {
                 return c >= '0' && c <= '9';
             });

tests/src/unit-json_pointer.cpp

@@ -1122,17 +1122,17 @@ TEST_CASE("flatten of structured values")
 
         // the same for other keys that are not valid array indices
         CHECK_THROWS_WITH_AS(json({{"/a/0", 1}, {"/a/1a", 2}}).unflatten(),
-                             "[json.exception.out_of_range.404] unresolved reference token '1a'", json::out_of_range&);
+        "[json.exception.out_of_range.404] unresolved reference token '1a'", json::out_of_range&);
         CHECK_THROWS_WITH_AS(json({{"/a/0", 1}, {"/a/-", 2}}).unflatten(),
-                             "[json.exception.out_of_range.404] unresolved reference token '-'", json::out_of_range&);
+        "[json.exception.out_of_range.404] unresolved reference token '-'", json::out_of_range&);
     }
 
     SECTION("unflatten with the empty token among array indices")
     {
         CHECK_THROWS_WITH_AS(json({{"/a/0", 1}, {"/a/", 2}}).unflatten(),
-                             "[json.exception.out_of_range.404] unresolved reference token ''", json::out_of_range&);
+        "[json.exception.out_of_range.404] unresolved reference token ''", json::out_of_range&);
         CHECK_THROWS_WITH_AS(json({{"/a/0", 1}, {"/a/1", 2}, {"/a/", 3}}).unflatten(),
-                             "[json.exception.out_of_range.404] unresolved reference token ''", json::out_of_range&);
+        "[json.exception.out_of_range.404] unresolved reference token ''", json::out_of_range&);
 
         // without an index "0", the empty token is an ordinary object key
         CHECK(json({{"/a/", 2}}).unflatten() == json({{"a", {{"", 2}}}}));