SERVER-99691: Throw when fromjson() doesn't parse the entire string (#32320)

GitOrigin-RevId: a7c707bc95ed2f80669aeeb93c8c11fe9cb985e2

Author: rsteinkeX

src/mongo/bson/json.cpp

@@ -110,6 +110,11 @@ std::string escapeNewlines(const char* input, int len) {
     }
     return out.str();
 }
+
+bool isAllSpace(StringData str) {
+    return std::all_of(str.begin(), str.end(), [](char c) { return ctype::isSpace(c); });
+}
+
 }  // namespace
 
 JParse::JParse(StringData str)
@@ -1554,14 +1559,14 @@ StatusWith<Date_t> JParse::parseDate() {
     return date;
 }
 
-BSONObj fromjson(const char* jsonString, int* len) {
+namespace fromjson_detail {
+
+BSONObj fromJsonImpl(const char* jsonString, size_t len) {
     MONGO_JSON_DEBUG("jsonString: " << jsonString);
-    if (jsonString[0] == '\0') {
-        if (len)
-            *len = 0;
+    if (len == 0) {
         return BSONObj();
     }
-    JParse jparse(jsonString);
+    JParse jparse(StringData{jsonString, len});
     BSONObjBuilder builder;
     Status ret = Status::OK();
     try {
@@ -1575,14 +1580,13 @@ BSONObj fromjson(const char* jsonString, int* len) {
     if (ret != Status::OK()) {
         uasserted(16619, "code {}: {}: {}"_format(ret.code(), ret.codeString(), ret.reason()));
     }
-    if (len)
-        *len = jparse.offset();
+    uassert(ErrorCodes::FailedToParse,
+            "Garbage at end of json string",
+            isAllSpace(jsonString + jparse.offset()));
     return builder.obj();
 }
 
-BSONObj fromjson(StringData str) {
-    return fromjson(str.toString().c_str());
-}
+}  // namespace fromjson_detail
 
 std::string tojson(const BSONObj& obj, JsonStringFormat format, bool pretty) {
     return obj.jsonString(format, pretty);

src/mongo/bson/json.h

@@ -40,6 +40,11 @@
 
 namespace mongo {
 
+namespace fromjson_detail {
+/** Private implementation detail of fromjson. */
+BSONObj fromJsonImpl(const char* jsonString, size_t len);
+}  // namespace fromjson_detail
+
 /**
  * Create a BSONObj from a JSON <http://www.json.org>,
  * <http://www.ietf.org/rfc/rfc4627.txt> string.  In addition to the JSON
@@ -49,14 +54,46 @@ namespace mongo {
  * used when specifying field names and std::string values instead of double
  * quotes.  JSON unicode escape sequences (of the form \uXXXX) are
  * converted to utf8.
+ * `str` must be a null terminated string.
+ *
+ * `str` must be completely consumed by the parse.
+ * Trailing whitespace is tolerated.
  *
- * @throws AssertionException if parsing fails.  The message included with
- * this assertion includes the character offset where parsing failed.
+ * Throws with `ErrorCodes::FailedToParse` on failure.
+ *   - If the parse failed because the `str` was incompletely consumed,
+ *     the exception message will indicate "Garbage at end".
+ *   - Otherwise, the message includes the character offset where parsing failed.
  */
-BSONObj fromjson(StringData str);
 
-/** @param len will be size of JSON object in text chars. */
-BSONObj fromjson(const char* str, int* len = nullptr);
+inline BSONObj fromjson(const char* str) {
+    return fromjson_detail::fromJsonImpl(str, strlen(str));
+}
+
+inline BSONObj fromjson(char* str) {
+    return fromjson_detail::fromJsonImpl(str, strlen(str));
+}
+
+inline BSONObj fromjson(const std::string& str) {
+    return fromjson_detail::fromJsonImpl(str.c_str(), str.size());
+}
+
+inline BSONObj fromjson(const str::stream& ss) {
+    return fromjson(std::string{ss});
+}
+
+/** Inefficiently promote to std::string, temporarily. */
+inline BSONObj fromjson(StringData str) {
+    return fromjson(std::string{str});
+}
+
+/** Decay arrays (literals) to `const char*`. */
+template <size_t N>
+BSONObj fromjson(const char (&str)[N]) {
+    return fromjson_detail::fromJsonImpl(str, N - 1);
+}
+
+/** Prevent conversion. Caller must choose a directly supported overload. */
+BSONObj fromjson(const auto& str) = delete;
 
 /**
  * Tests whether the JSON string is an Array.

src/mongo/unittest/death_test.cpp

@@ -325,17 +325,11 @@ void DeathTestBase::Subprocess::monitorChild(FILE* pf) {
             line = line.substr(0, line.size() - 1);
         if (line.empty())
             continue;
-        int parsedLen = 0;
-        BSONObj parsedChildLog;
         try {
-            parsedChildLog = fromjson(lineBuf, &parsedLen);
+            auto parsedChildLog = fromjson(lineBuf);
+            LOGV2(20165, "child", "json"_attr = parsedChildLog);
         } catch (DBException&) {
             // ignore json parsing errors and dump the whole log line as text
-            parsedLen = 0;
-        }
-        if (static_cast<size_t>(parsedLen) == line.size()) {
-            LOGV2(20165, "child", "json"_attr = parsedChildLog);
-        } else {
             LOGV2(20169, "child", "text"_attr = line);
         }
         os.write(lineBuf, bytesRead);