fix: cast to json unknown 65535 error and add ut cases

[dapan1121]

Description

Issue(s)

• Close/close/Fix/fix/Resolve/resolve: Issue Link

Checklist

Please check the items in the checklist if applicable.

• Is the user manual updated?
• Are the test cases passed and automated?
• Is there no significant decrease in test coverage?

[gemini-code-assist]

Code Review

This pull request prevents 'Unknown error 65535' by explicitly disallowing casts to JSON and improving error code propagation in scalar functions. It also updates the executor to correctly expand constant arguments for indefinite-rows functions and refines node type resolution for row-count placeholders. Feedback was provided to include a NULL check for expression pointers in the executor to improve robustness against potential crashes.

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source/libs/executor/src/executorInt.c (383-387)

Accessing pOneExpr->pExpr without a NULL check could lead to a crash if the expression node is not initialized. While it is generally expected to be valid in the executor context, adding a safety check before accessing nodeType and _function is a best practice for robustness.

        if (!needDummyCol && j == 0 && pOneExpr->pExpr != NULL &&
            pOneExpr->pExpr->nodeType == QUERY_NODE_FUNCTION &&
            fmIsIndefiniteRowsFunc(pOneExpr->pExpr->_function.functionId)) {
          needDummyCol = true;
        }

[Copilot]

Pull request overview

Fixes the “CAST(... AS JSON) -> Unknown error 65535” behavior by returning a deterministic, user-facing error during translation/runtime, and adds regression coverage in both Python system tests and C++ scalar unit tests. Also includes small scalar/executor adjustments related to constant/placeholder node typing and constant-arg handling for indefinite-rows functions.

Changes:

• Reject CAST(expr AS JSON) during function translation and avoid propagating TSDB_CODE_FAILED as “Unknown error 65535”.
• Make castFunction() return TSDB_CODE_SCALAR_CONVERT_ERROR for unsupported output types instead of TSDB_CODE_FAILED.
• Add regression tests (Python SQLSmith repro list + C++ unit test) and adjust scalar/executor handling for LEFT_VALUE typing and constant expansion for indefinite-rows functions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/cases/11-Functions/01-Scalar/test_fun_sca_cast.py	Adds SQLSmith-style regression coverage for CAST-to-JSON error behavior.
source/libs/scalar/test/scalar/scalarTests.cpp	Adds a unit test asserting castFunction() returns TSDB_CODE_SCALAR_CONVERT_ERROR when output type is JSON.
source/libs/scalar/src/sclfunc.c	Changes default cast output-type handling to return TSDB_CODE_SCALAR_CONVERT_ERROR.
source/libs/scalar/src/scalar.c	Adds explicit type resolution for QUERY_NODE_LEFT_VALUE using operator result type.
source/libs/function/src/builtins.c	Rejects CAST(... AS JSON) at translation time with a descriptive message.
source/libs/executor/src/executorInt.c	Refines dummy-column creation logic for constant parameters, especially for indefinite-rows functions’ first argument.

Comments suppressed due to low confidence (1)

test/cases/11-Functions/01-Scalar/test_fun_sca_cast.py:1524

• do_cast_to_json_invalid() calls tdSql.error(...) but never inspects the returned error_info, so the test will still pass if the server returns the exact regression you're trying to prevent ("Unknown error 65535"). Capture the returned error string (or pass expectErrInfo/expectedErrno) and assert it does not contain "Unknown error 65535" (and ideally matches the expected CAST-to-JSON rejection message).

        # All of the following must return a proper error (not Unknown error 65535)
        tdSql.error("select n, si from t3 where c1 > 2.97 order by ((-ubi) % f) % (-22) asc nulls last, cast(ti as json) desc nulls last limit 12 offset 33;")
        tdSql.error("select bi, ubi, ubi from t2 order by cast(-pow(usi, floor(pow(id, f))) as json) desc nulls last;")
        tdSql.error("select c1 from t1 order by +(-(-f)) asc nulls last, cast(position('s_431' in upper(a)) as json) asc nulls last limit 50 offset 43;")
        tdSql.error("select usi, vb from t1 where usi > 6 order by cast(v as json) asc nulls last limit 5 offset 45;")
        tdSql.error("select v from t2 order by cast(pow(abs(bi), d) & ti as json) asc nulls last;")

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