♻️ allow patch and diff to be used with arbitrary string types (#4536)

tests/src/unit-alt-string.cpp

@@ -35,10 +35,21 @@ class alt_string
     alt_string(size_t count, char chr): str_impl(count, chr) {}
     alt_string() = default;
 
-    template <typename...TParams>
-    alt_string& append(TParams&& ...params)
+    alt_string& append(char ch)
     {
-        str_impl.append(std::forward<TParams>(params)...);
+        str_impl.push_back(ch);
+        return *this;
+    }
+
+    alt_string& append(const alt_string& str)
+    {
+        str_impl.append(str.str_impl);
+        return *this;
+    }
+
+    alt_string& append(const char* s, std::size_t length)
+    {
+        str_impl.append(s, length);
         return *this;
     }
 
@@ -157,6 +168,11 @@ class alt_string
         return *this;
     }
 
+    void reserve( std::size_t new_cap = 0 )
+    {
+        str_impl.reserve(new_cap);
+    }
+
   private:
     std::string str_impl {}; // NOLINT(readability-redundant-member-init)
 
@@ -319,4 +335,28 @@ TEST_CASE("alternative string type")
         CHECK(j.at(alt_json::json_pointer("/foo/0")) == j["foo"][0]);
         CHECK(j.at(alt_json::json_pointer("/foo/1")) == j["foo"][1]);
     }
+
+    SECTION("patch")
+    {
+        alt_json const patch1 = alt_json::parse(R"([{ "op": "add", "path": "/a/b", "value": [ "foo", "bar" ] }])");
+        alt_json const doc1 = alt_json::parse(R"({ "a": { "foo": 1 } })");
+
+        CHECK_NOTHROW(doc1.patch(patch1));
+        alt_json doc1_ans = alt_json::parse(R"(
+                {
+                    "a": {
+                        "foo": 1,
+                        "b": [ "foo", "bar" ]
+                    }
+                }
+            )");
+        CHECK(doc1.patch(patch1) == doc1_ans);
+    }
+
+    SECTION("diff")
+    {
+        alt_json const j1 = {"foo", "bar", "baz"};
+        alt_json const j2 = {"foo", "bam"};
+        CHECK(alt_json::diff(j1, j2).dump() == "[{\"op\":\"replace\",\"path\":\"/1\",\"value\":\"bam\"},{\"op\":\"remove\",\"path\":\"/2\"}]");
+    }
 }