JSON5 Multi-line Strings with Tab Characters Cause SQLite Malformed JSON Error

JSON5 Multi-line Strings with Tab Characters and SQLite Parsing Behavior

The core issue revolves around SQLite’s handling of JSON5-formatted strings, specifically when multi-line strings contain tab characters for indentation. JSON5 is an extension of JSON that allows for more flexible syntax, including multi-line strings and additional whitespace characters. However, SQLite’s JSON parser appears to reject JSON5 strings that include tab characters within multi-line strings, throwing a "malformed JSON" error. This behavior contradicts the expectations set by the JSON5 specification and other tooling that supports JSON5 parsing.

The JSON5 specification explicitly permits additional whitespace characters, including tabs, outside of string literals. However, the specification does not clearly define whether tabs within multi-line strings should be treated as valid content or ignored. This ambiguity has led to confusion and inconsistencies in how different parsers, including SQLite’s, handle such cases. The issue is further complicated by the fact that SQLite’s JSON parser inherits some restrictions from the original JSON specification, which disallows control characters (including tabs) within strings unless they are escaped.

Misalignment Between JSON5 Specification and SQLite’s JSON Parser

The root cause of the issue lies in the misalignment between the JSON5 specification and SQLite’s JSON parser implementation. While the JSON5 specification allows for more lenient syntax, SQLite’s parser adheres to stricter rules inherited from the original JSON specification. Specifically, the original JSON specification disallows control characters, such as tabs, within strings unless they are escaped. SQLite’s JSON parser appears to enforce this rule even when parsing JSON5 content, leading to the rejection of valid JSON5 strings that contain unescaped tab characters within multi-line strings.

The JSON5 specification does not explicitly state that tabs within multi-line strings should be stripped or ignored. Instead, it allows for additional whitespace characters outside of strings and permits multi-line strings with escaped newline characters. This creates a gray area where the interpretation of tabs within multi-line strings is left to the discretion of the parser implementation. SQLite’s parser, in this case, interprets tabs within multi-line strings as invalid control characters, resulting in a "malformed JSON" error.

Furthermore, the issue is exacerbated by the fact that other JSON5 parsers and tooling may handle tabs within multi-line strings differently, leading to inconsistencies across platforms. This discrepancy highlights the need for a clear and unambiguous definition of how tabs and other whitespace characters should be handled within JSON5 strings, particularly in the context of multi-line strings.

Resolving the Issue: Testing with Updated SQLite Builds and Workarounds

To address the issue, the SQLite development team has released an updated build that modifies the JSON parser to accept hard tabs within string literals. This change aligns SQLite’s JSON parser more closely with the JSON5 specification and resolves the "malformed JSON" error when parsing JSON5 strings with tab characters. Users experiencing this issue are encouraged to test their applications with the updated SQLite build (check-in 380f09c194caff55 or later) to verify whether the problem is resolved.

For users who cannot immediately update to the latest SQLite build, a temporary workaround involves stripping leading tabs from lines within multi-line strings before passing the JSON5 content to SQLite’s JSON parser. This can be achieved using a regular expression, such as /(?<=\\\n)\t+/g, to remove tab characters following line continuations. While this workaround is not ideal, it allows users to continue working with JSON5 content that includes tab characters until they can update to a version of SQLite that fully supports JSON5 syntax.

In addition to testing the updated SQLite build, users should also review their JSON5 content to ensure compliance with the JSON5 specification. This includes verifying that multi-line strings are properly formatted and that any necessary escaping is applied to control characters. By taking these steps, users can avoid potential issues with JSON5 parsing and ensure consistent behavior across different platforms and tooling.

In conclusion, the issue of SQLite rejecting JSON5 strings with tab characters within multi-line strings stems from a misalignment between the JSON5 specification and SQLite’s JSON parser implementation. The SQLite development team has addressed this issue in an updated build, and users are encouraged to test their applications with the latest version. For those unable to update immediately, a temporary workaround is available to strip leading tabs from multi-line strings. By understanding the underlying causes and applying the appropriate solutions, users can resolve this issue and ensure smooth parsing of JSON5 content in SQLite.