fix: custom plot charts function should error on invalid chart types

[willkill07]

Description

The original behavior was to fall back to a line chart. Instead, we should raise an error.

Also improves configuration for the example function.

Closes nvbugs-5566144

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Summary by CodeRabbit

• New Features

  • Clearer validation and error messages when an unsupported chart type is requested.
  • Configuration options now include descriptive metadata and sensible defaults.

• Refactor

  • Streamlined chart type resolution with earlier detection and consistent canonical types.
  • Behavior change: invalid chart requests now error out instead of defaulting to a first available type.

• Bug Fixes

  • Prevents unintended chart selection by enforcing explicit, supported chart types.

[coderabbitai]

Walkthrough

Refactors chart type determination to canonical mapping with strict validation and error on unsupported types. Updates workflow config to use Field metadata and LLMRef, and restructures chart creation via a mapping lookup. Resolves chart type before data loading and unifies chart generation logic.

Changes

Cohort / File(s)	Summary of Changes
Chart type resolution and validation examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py	Replaced permissive defaulting with canonical type resolution (line/bar/scatter) and strict validation against available types; raises ValueError on unsupported requests; simplified control flow into a single resolution path.
Workflow config and chart creation refactor examples/custom_functions/plot_charts/src/nat_plot_charts/register.py	Converted PlotChartsWorkflowConfig fields to use Field with descriptions/defaults; changed llm_name type to LLMRef. Moved chart_type resolution earlier; replaced if/elif chart creation with mapping lookup and added unsupported-type validation; retained error handling.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant U as User
  participant WF as PlotCharts Workflow
  participant DT as determine_chart_type
  participant CG as Chart Generator

  U->>WF: input_message (requested chart type + data refs)
  WF->>DT: resolve chart_type(requested_type, available_types)
  alt supported type
    DT-->>WF: chart_type
    note right of WF: Chart type resolved before data load
    WF->>CG: create_function_mapping[chart_type](data, config)
    CG-->>WF: chart artifact (path/figure)
    WF-->>U: success (description + output file)
  else unsupported type
    DT-->>WF: error (ValueError with original request)
    WF-->>U: error response
  end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested labels

breaking

Pre-merge checks and finishing touches

Important

Pre-merge checks failed

Please resolve all errors before merging. Addressing warnings is optional.

❌ Failed checks (1 error)

Check name	Status	Explanation	Resolution
Title Check	❌ Error	The title clearly summarizes the fix and is under the 72-character limit, but it uses the phrasing “should error” instead of the imperative form. The style guideline requires titles written as commands in imperative mood. Therefore, it does not fully comply with the title requirements.	Please rephrase the title into imperative mood, for example “Fix custom plot charts function to error on invalid chart types.”

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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Actionable comments posted: 1

📜 Review details

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Review profile: CHILL

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📥 Commits

Reviewing files that changed from the base of the PR and between 299561f and f4e3cc8.

📒 Files selected for processing (2)

• examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py (1 hunks)
• examples/custom_functions/plot_charts/src/nat_plot_charts/register.py (3 hunks)

🧰 Additional context used

📓 Path-based instructions (4)

**/*.{py,yaml,yml}

📄 CodeRabbit inference engine (.cursor/rules/nat-test-llm.mdc)

**/*.{py,yaml,yml}: Configure response_seq as a list of strings; values cycle per call, and [] yields an empty string.
Configure delay_ms to inject per-call artificial latency in milliseconds for nat_test_llm.

Files:

• examples/custom_functions/plot_charts/src/nat_plot_charts/register.py
• examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py

**/*.py

📄 CodeRabbit inference engine (.cursor/rules/nat-test-llm.mdc)

**/*.py: Programmatic use: create TestLLMConfig(response_seq=[...], delay_ms=...), add with builder.add_llm("", cfg).
When retrieving the test LLM wrapper, use builder.get_llm(name, wrapper_type=LLMFrameworkEnum.) and call the framework’s method (e.g., ainvoke, achat, call).

**/*.py: In code comments/identifiers use NAT abbreviations as specified: nat for API namespace/CLI, nvidia-nat for package name, NAT for env var prefixes; do not use these abbreviations in documentation
Follow PEP 20 and PEP 8; run yapf with column_limit=120; use 4-space indentation; end files with a single trailing newline
Run ruff check --fix as linter (not formatter) using pyproject.toml config; fix warnings unless explicitly ignored
Respect naming: snake_case for functions/variables, PascalCase for classes, UPPER_CASE for constants
Treat pyright warnings as errors during development
Exception handling: use bare raise to re-raise; log with logger.error() when re-raising to avoid duplicate stack traces; use logger.exception() when catching without re-raising
Provide Google-style docstrings for every public module, class, function, and CLI command; first line concise and ending with a period; surround code entities with backticks
Validate and sanitize all user input, especially in web or CLI interfaces
Prefer httpx with SSL verification enabled by default and follow OWASP Top-10 recommendations
Use async/await for I/O-bound work; profile CPU-heavy paths with cProfile or mprof before optimizing; cache expensive computations with functools.lru_cache or external cache; leverage NumPy vectorized operations when beneficial

Files:

• examples/custom_functions/plot_charts/src/nat_plot_charts/register.py
• examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py

**/*

⚙️ CodeRabbit configuration file

**/*: # Code Review Instructions

• Ensure the code follows best practices and coding standards. - For Python code, follow
  PEP 20 and
  PEP 8 for style guidelines.
• Check for security vulnerabilities and potential issues. - Python methods should use type hints for all parameters and return values.
  Example:

  def my_function(param1: int, param2: str) -> bool:
      pass

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    and use logger.error() (not logger.exception()) to avoid duplicate stack trace output.
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words listed in the ci/vale/styles/config/vocabularies/nat/reject.txt file, words that might appear to be
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Files:

• examples/custom_functions/plot_charts/src/nat_plot_charts/register.py
• examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py

examples/**/*

⚙️ CodeRabbit configuration file

examples/**/*: - This directory contains example code and usage scenarios for the toolkit, at a minimum an example should
contain a README.md or file README.ipynb.

• If an example contains Python code, it should be placed in a subdirectory named src/ and should
  contain a pyproject.toml file. Optionally, it might also contain scripts in a scripts/ directory.
• If an example contains YAML files, they should be placed in a subdirectory named configs/. - If an example contains sample data files, they should be placed in a subdirectory named data/, and should
  be checked into git-lfs.

Files:

• examples/custom_functions/plot_charts/src/nat_plot_charts/register.py
• examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py

🧬 Code graph analysis (1)

examples/custom_functions/plot_charts/src/nat_plot_charts/register.py (3)

src/nat/data_models/component_ref.py (1)

• LLMRef (116-124)

src/nat/data_models/function.py (1)

• FunctionBaseConfig (26-27)

examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py (4)

• determine_chart_type (153-169)
• create_line_plot (60-82)
• create_bar_plot (85-118)
• create_scatter_plot (121-150)

🪛 Ruff (0.13.3)

examples/custom_functions/plot_charts/src/nat_plot_charts/plot_chat.py

169-169: Avoid specifying long messages outside the exception class

(TRY003)

[willkill07]

/merge