rainerscript: add append_json() function by 20syldev · Pull Request #6385 · rsyslog/rsyslog

20syldev · 2025-12-23T14:42:26Z

Summary

Users need to dynamically build JSON arrays and objects by adding elements without external processing or complex workarounds.

Notes

Tests included: rscript_append_json.sh and rscript_append_json-vg.sh
Documentation added: doc/source/rainerscript/functions/rs-append_json.rst

Impact: New RainerScript function available to all users.

Before: No native way to append elements to JSON arrays/objects in RainerScript.
After: append_json(array, element) or append_json(object, key, value) returns a new JSON structure with the element/property added.

gemini-code-assist · 2025-12-23T14:42:42Z

Summary of Changes

Hello @20syldev, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances RainerScript's JSON manipulation capabilities by introducing a new append_json() function. This function provides a native way for users to dynamically modify JSON arrays by appending elements or JSON objects by adding key-value pairs. It addresses the previous lack of such functionality, allowing for more flexible and efficient JSON processing within RainerScript configurations. The implementation ensures that the original JSON structure remains unchanged, as the function returns a newly constructed JSON object or array.

Highlights

New Function: append_json(): Introduces a new RainerScript function, append_json(), to dynamically build JSON arrays and objects.
JSON Array Manipulation: Allows appending an element to a JSON array, returning a new array with the added element.
JSON Object Manipulation: Enables adding a key-value pair to a JSON object, returning a new object with the new property.
Immutability: The append_json() function always returns a new JSON structure, ensuring the original input JSON is not modified.
Comprehensive Testing and Documentation: Includes new test scripts (rscript_append_json.sh, rscript_append_json-vg.sh) and dedicated documentation (rs-append_json.rst) for the new function.

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gemini-code-assist

Code Review

This pull request introduces a new and useful append_json function to RainerScript. The implementation is mostly sound, but I've identified several critical and high-severity issues related to memory management, particularly in error-handling paths. There are multiple potential memory leaks if json-c library calls fail, and a potential crash due to an unhandled NULL return from var2CString. I've also included suggestions for a minor refactoring to reduce code duplication and for expanding the test suite to cover more use cases for this new function.

grammar/rainerscript.c

tests/rscript_append_json.sh

gemini-code-assist

Code Review

This pull request introduces a new append_json() function to RainerScript, which is a valuable addition for dynamic JSON manipulation. The implementation is mostly correct, but there are a few critical issues related to memory management and error handling when using the json-c library that could lead to memory leaks or incorrect behavior under error conditions (like out-of-memory). The provided comments offer suggestions to improve the robustness of the implementation by using safer json-c functions and adding proper error handling. Additionally, expanding the test suite to cover more use cases and edge cases for the new function is recommended.

grammar/rainerscript.c

tests/rscript_append_json.sh

gemini-code-assist

Code Review

This pull request introduces a useful append_json function to RainerScript for manipulating JSON data. The implementation is mostly solid, with accompanying documentation and tests. However, I've identified a couple of critical memory leak issues in the object-handling logic due to missing error checks, which could lead to instability under certain conditions. I've also provided a suggestion to improve the array-handling code for better maintainability. Addressing these points will make the new function more robust.

grammar/rainerscript.c

rgerhards · 2025-12-26T10:41:49Z

@20syldev looks like this needs a rebase (not merge)

20syldev · 2025-12-26T19:49:42Z

@20syldev looks like this needs a rebase (not merge)

Done!

gemini-code-assist

Code Review

This pull request introduces a new append_json() function to RainerScript, which is a great addition for dynamically manipulating JSON data. The implementation is mostly correct and includes documentation and tests.

My review focuses on improving the robustness and maintainability of the C implementation in grammar/rainerscript.c. I've identified a critical issue where silent failures during JSON object creation could lead to data loss. I've also suggested refactoring the error handling to align with the project's established conventions and improving variable scoping for better readability.

The documentation and test cases are well-written and cover the intended functionality. Addressing the feedback will make the new function more reliable.

grammar/rainerscript.c

gemini-code-assist

Code Review

This pull request introduces a new RainerScript function, append_json(), which allows users to dynamically add elements to JSON arrays and properties to JSON objects. The implementation is accompanied by documentation and tests. The overall approach is sound, creating a new JSON object to ensure immutability of the original. However, I've identified two potential memory leaks in the object-handling logic due to the use of a deprecated json-c function that doesn't report errors. My review includes suggestions to fix these issues by using the recommended _ex version of the function and adding proper error handling, consistently applying the finalize_it: label for error management as per rsyslog policies.

grammar/rainerscript.c

rgerhards

I can make the adjustments myself, but would appreciate if you could do them.

tests/Makefile.am

tests/rscript_append_json-vg.sh

gemini-code-assist

Code Review

This pull request introduces a new append_json() function to RainerScript, allowing users to add elements to JSON arrays and properties to JSON objects. The implementation is well-structured and includes documentation and tests. My review focuses on improving the robustness and safety of the new C function. The main suggestions are to use json_object_deep_copy to prevent side-effects from shared mutable objects, to make type checking more explicit and robust, and to ensure error handling aligns with rsyslog policies.

grammar/rainerscript.c

20syldev · 2026-01-02T17:41:28Z

Please let me know if any of the issues I marked as “Resolved” are possible, as I haven't figured out how to do it with libfastjson.

rgerhards

I added comments to the AI review. Once this is through, I can do a manual round of review.

rgerhards · 2026-01-05T09:32:02Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces a new and useful RainerScript function, append_json(), for dynamically building JSON arrays and objects. The implementation is well-structured, and the inclusion of documentation and tests is commendable. I've identified a critical compilation issue due to a likely function name typo, a high-severity issue related to a potential memory leak from an unchecked return value (with a reminder to align with rsyslog error handling policies), and a medium-severity suggestion to refactor some duplicated code for better maintainability. Addressing these points will make this a solid contribution.

grammar/rainerscript.c

rgerhards · 2026-01-12T17:02:59Z

@20syldev my bad, I had a wrong merge order. I'll see that I can rebase it.

20syldev · 2026-01-12T17:09:25Z

@20syldev my bad, I had a wrong merge order. I'll see that I can rebase it.

No problem

Users need to parse delimited strings (CSV, tags, paths) into arrays for iteration or JSON output without external processing. Impact: New RainerScript function available to all users. Before: No native way to split strings into arrays in RainerScript. After: split(string, separator) returns a JSON array of substrings. Technical overview: Implements doFunct_split() in grammar/rainerscript.c Registers "split" in scriptFunct table with 2 required args Adds CNFFUNC_SPLIT enum in rainerscript.h Uses unified strstr-based iteration for all separator lengths Handles edge cases: empty input, leading/trailing/consecutive delimiters Includes error handling for json-c memory allocation failures Returns empty JSON array on null/empty input or separator Includes documentation (rs-split.rst) and test scripts

rgerhards · 2026-01-13T08:21:30Z

CI fail is a know and unrelated flake

20syldev · 2026-01-13T23:38:34Z

CI fail is a know and unrelated flake

Great, I was wondering about that. Thanks for the merge!

20syldev · 2026-01-17T00:33:18Z

@rgerhards Hi, I just noticed that the commit message was copied incorrectly for append_json. Here is the correct one:

Title:

rainerscript: add append_json() function

Description:

Users need to dynamically build JSON arrays and objects by adding
elements without external processing or complex workarounds.

Impact: New RainerScript function available to all users.

Before: No native way to append elements to JSON arrays/objects in RainerScript.
After: append_json(array, element) or append_json(object, key, value) returns
a new JSON structure with the element/property added.

Technical overview:
Implements doFunct_append() in grammar/rainerscript.c
Registers "append_json" in scriptFunct table with 2-3 args
Adds CNFFUNC_APPEND_JSON enum in rainerscript.h
Supports both JSON arrays (2 args) and objects (3 args)
Returns new object (functional style, original unchanged)
Uses json_object_iter API for object copying
Handles edge cases: null input, non-JSON input, memory allocation failures
Includes documentation (rs-append_json.rst) and test scripts

rgerhards · 2026-01-17T09:51:22Z

sry for that, but now it's too late. It is impossible to change commit afterwards.

20syldev · 2026-01-17T10:11:42Z

sry for that, but now it's too late. It is impossible to change commit afterwards.

Okay, I understand!

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20syldev force-pushed the append_json branch from 4fdd4f2 to 9c661f9 Compare December 23, 2025 18:53

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rgerhards self-assigned this Dec 24, 2025

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20syldev force-pushed the append_json branch from 9c661f9 to 6e2bb38 Compare December 24, 2025 10:31

20syldev force-pushed the append_json branch from 6e2bb38 to 20d0e11 Compare December 26, 2025 19:48

20syldev marked this pull request as ready for review December 26, 2025 19:50

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20syldev changed the title ~~wip: rainerscript: add append_json() function~~ rainerscript: add append_json() function Dec 28, 2025

20syldev force-pushed the append_json branch from 20d0e11 to be58266 Compare December 28, 2025 19:06

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20syldev force-pushed the append_json branch from be58266 to 6dec92b Compare January 2, 2026 14:21

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20syldev force-pushed the append_json branch from 6dec92b to a3d6d8a Compare January 2, 2026 17:38

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20syldev force-pushed the append_json branch from a3d6d8a to bb22fe1 Compare January 5, 2026 09:28

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20syldev force-pushed the append_json branch from bb22fe1 to 2221741 Compare January 8, 2026 08:21

rgerhards added enhancement do_first Things that should be done very soon,usually used for things that did not make it into prev release. labels Jan 12, 2026

rgerhards force-pushed the append_json branch from 2221741 to ef050ae Compare January 12, 2026 17:35

rgerhards approved these changes Jan 12, 2026

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rgerhards merged commit 98c8394 into rsyslog:main Jan 13, 2026
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20syldev deleted the append_json branch January 13, 2026 23:38

20syldev restored the append_json branch January 17, 2026 00:26

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20syldev commented Dec 23, 2025

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rgerhards commented Dec 26, 2025

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20syldev commented Jan 2, 2026

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rgerhards commented Jan 17, 2026 •

edited

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