[professor-moody]

Summary

This change hardens JSON text generation in src/idl_gen_text.cpp and path/case utilities in src/util.cpp:

• JsonPrinter::GenFieldOffset (src/idl_gen_text.cpp): Call flexbuffers::VerifyBuffer(vec->data(), vec->size()) before flexbuffers::GetRoot(vec->data(), vec->size()) when formatting flexbuffer byte-vector fields with opts.json_nested_flexbuffers, returning "invalid nested flexbuffer" on malformed nested buffers.
• JsonPrinter::PrintOffset (src/idl_gen_text.cpp): Check if (index >= type_vec->size()) return "union type vector too short"; before calling type_vec->Get(index) on union vectors so out-of-bounds union type lookups fail cleanly.
• GenerateTextFromTable (src/idl_gen_text.cpp): Return GenTextFromTable(parser, table, table_name, _text) == nullptr so the boolean wrapper returns true on success and false on error.
• RelativeToRootPath and case-conversion helpers (src/util.cpp): Guard against empty absolute_project or absolute_filepath before calling absolute_project.back() or absolute_filepath.substr(common_prefix_len + 1) in RelativeToRootPath, and cast char inputs to unsigned char before calling C character classification functions (islower, isdigit, isalpha) in ToSnakeCase, CamelToSnake, ToDasher, and SnakeToSnake2.

Verification

• Added positive control and negative regression tests in tests/json_test.cpp (JsonUnionStructTest) covering nested FlexBuffers, truncated union type vectors, GenerateTextFromTable, portable RelativeToRootPath expectations, and ConvertCase high-bit inputs.
• The recorded full, unfiltered flattests run reports ALL TESTS PASSED and exit code 0 with the patch. The recorded baseline run exits 1. The logs do not establish a registered-test count or a Windows test result.

Scope and related work

These checks provide targeted validation within text generation. Validation of the enclosing FlatBuffer remains a caller responsibility.

PR #9308 handles absent scalar union type metadata in the same printer and test files. That change is outside this patch's retained scope. PR #9207 changes make-dependency escaping in the text generator and utility file; PR #9270 changes locale initialization in the utility file. These open changes share files, so integration still requires review even though the retained changes have different purposes.

The packet includes a hash-bound hunk-level prior-art scope supersession receipt that links the current patch to the earlier reviewed patch and records removal of the overlapping scalar union-discriminator hunks.