fix(error-handling): handle json.JSONDecodeError in robot.json_helper.parse_json #2811

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opened 2026-04-04 20:35:04 +00:00 by freemo · 0 comments

freemo commented

2026-04-04 20:35:04 +00:00

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Metadata

Branch: fix/v3.8.0-json-helper-decode-error
Commit Message: fix(error-handling): handle json.JSONDecodeError in robot.json_helper.parse_json
Milestone: v3.8.0
Parent Epic: #362

Background and context

The parse_json function in robot/json_helper.py calls json.loads without any error handling. If a test case passes a malformed or invalid JSON string to this function, a json.JSONDecodeError will propagate uncaught, crashing the test case unexpectedly. This was discovered during a bug-hunt audit of the robot/ helper layer.

Per CONTRIBUTING.md's error-handling guidelines, exceptions should only be caught when they can be meaningfully handled. In this case, the function is a low-level parsing utility used by Robot Framework test cases — an unhandled decode error here provides no useful diagnostic context to the test runner and causes an abrupt, confusing failure.

Current behavior (for bugs)

When parse_json receives an invalid JSON string (e.g., "not json"), json.loads raises json.JSONDecodeError, which propagates uncaught out of the function and crashes the calling test case.

# robot/json_helper.py — lines 6–8
def parse_json(json_string):
    """Parse a JSON string and return as a dictionary."""
    return json.loads(json_string)

Reproduction steps:

Call parse_json("invalid json string") from any Robot Framework test.
Observe json.JSONDecodeError raised and test case aborted.

Expected behavior

The function should catch json.JSONDecodeError and either:

Return None to signal a parse failure without crashing, or
Re-raise as a more descriptive, domain-specific exception with context about the bad input.

The chosen approach must be consistent with the project's fail-fast principles while still providing a meaningful signal to callers.

Acceptance criteria

parse_json no longer raises an unhandled json.JSONDecodeError when given invalid input
The chosen error-handling strategy (return None or raise domain exception) is documented in the function's docstring
A unit test covers the invalid-JSON code path and asserts the expected return value or exception type
A Robot Framework test scenario covers the invalid-JSON code path
nox (all default sessions) passes with no errors
Coverage >= 97%

Supporting information

File: robot/json_helper.py
Function: parse_json
Lines: 6–8
Related Epic: #362 — Security & Safety Hardening (covers explicit exception handling)
Severity: Medium — test cases may crash on malformed test data

Subtasks

Investigate whether callers of parse_json expect None or a raised exception on bad input
Implement try/except json.JSONDecodeError block in parse_json with the agreed-upon strategy
Update the function's docstring to document the error-handling behaviour
Tests (Unit): Add test for parse_json with invalid JSON input asserting correct behaviour
Tests (Robot): Add Robot Framework scenario for invalid JSON input to parse_json
Verify coverage >= 97% via nox -s coverage_report
Run nox (all default sessions), fix any errors

Definition of Done

This issue is complete when:

All subtasks above are completed and checked off.
A Git commit is created where the first line of the commit message matches the Commit Message in Metadata exactly, followed by a blank line, then additional lines providing relevant details about the implementation.
The commit is pushed to the remote on the branch matching the Branch in Metadata exactly.
The commit is submitted as a pull request to master, reviewed, and merged before this issue is marked done.
All nox stages pass.
Coverage >= 97%.

Automated by CleverAgents Bot
Supervisor: UAT Testing | Agent: ca-new-issue-creator

## Metadata - **Branch**: `fix/v3.8.0-json-helper-decode-error` - **Commit Message**: `fix(error-handling): handle json.JSONDecodeError in robot.json_helper.parse_json` - **Milestone**: v3.8.0 - **Parent Epic**: #362 ## Background and context The `parse_json` function in `robot/json_helper.py` calls `json.loads` without any error handling. If a test case passes a malformed or invalid JSON string to this function, a `json.JSONDecodeError` will propagate uncaught, crashing the test case unexpectedly. This was discovered during a bug-hunt audit of the `robot/` helper layer. Per CONTRIBUTING.md's error-handling guidelines, exceptions should only be caught when they can be meaningfully handled. In this case, the function is a low-level parsing utility used by Robot Framework test cases — an unhandled decode error here provides no useful diagnostic context to the test runner and causes an abrupt, confusing failure. ## Current behavior (for bugs) When `parse_json` receives an invalid JSON string (e.g., `"not json"`), `json.loads` raises `json.JSONDecodeError`, which propagates uncaught out of the function and crashes the calling test case. ```python # robot/json_helper.py — lines 6–8 def parse_json(json_string): """Parse a JSON string and return as a dictionary.""" return json.loads(json_string) ``` **Reproduction steps:** 1. Call `parse_json("invalid json string")` from any Robot Framework test. 2. Observe `json.JSONDecodeError` raised and test case aborted. ## Expected behavior The function should catch `json.JSONDecodeError` and either: - Return `None` to signal a parse failure without crashing, **or** - Re-raise as a more descriptive, domain-specific exception with context about the bad input. The chosen approach must be consistent with the project's fail-fast principles while still providing a meaningful signal to callers. ## Acceptance criteria - [ ] `parse_json` no longer raises an unhandled `json.JSONDecodeError` when given invalid input - [ ] The chosen error-handling strategy (return `None` or raise domain exception) is documented in the function's docstring - [ ] A unit test covers the invalid-JSON code path and asserts the expected return value or exception type - [ ] A Robot Framework test scenario covers the invalid-JSON code path - [ ] `nox` (all default sessions) passes with no errors - [ ] Coverage >= 97% ## Supporting information - **File**: `robot/json_helper.py` - **Function**: `parse_json` - **Lines**: 6–8 - **Related Epic**: #362 — Security & Safety Hardening (covers explicit exception handling) - **Severity**: Medium — test cases may crash on malformed test data ## Subtasks - [ ] Investigate whether callers of `parse_json` expect `None` or a raised exception on bad input - [ ] Implement `try/except json.JSONDecodeError` block in `parse_json` with the agreed-upon strategy - [ ] Update the function's docstring to document the error-handling behaviour - [ ] Tests (Unit): Add test for `parse_json` with invalid JSON input asserting correct behaviour - [ ] Tests (Robot): Add Robot Framework scenario for invalid JSON input to `parse_json` - [ ] Verify coverage >= 97% via `nox -s coverage_report` - [ ] Run `nox` (all default sessions), fix any errors ## Definition of Done This issue is complete when: - All subtasks above are completed and checked off. - A Git commit is created where the **first line** of the commit message matches the Commit Message in Metadata exactly, followed by a blank line, then additional lines providing relevant details about the implementation. - The commit is pushed to the remote on the branch matching the **Branch** in Metadata exactly. - The commit is submitted as a **pull request** to `master`, reviewed, and **merged** before this issue is marked done. - All nox stages pass. - Coverage >= 97%. --- **Automated by CleverAgents Bot** Supervisor: UAT Testing | Agent: ca-new-issue-creator

freemo added this to the v3.8.0 milestone

2026-04-04 20:35:09 +00:00

freemo added a new dependency

2026-04-04 20:35:18 +00:00

#362 Epic: Security & Safety Hardening

freemo added the

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label

2026-04-04 20:41:09 +00:00

freemo referenced this issue

2026-04-04 20:41:23 +00:00