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PylintScriptRule

Runs the full pylint static analyzer over every Python script embedded in a Perspective view.json — event handlers, message handlers, custom methods, and transform scripts. This is the project's primary defense against script bugs that would otherwise only show up at runtime in the Ignition gateway.

Severity: error by default for Fatal and Error pylint categories; warning for Warning, Convention, and Refactor. Each category can be remapped independently via category_mapping.

Auto-fix: Yes, for trailing whitespace (C0303 only). Other pylint findings are reported but not auto-fixed.

Basic config​

The simplest setup — accept the defaults:

{
  "PylintScriptRule": {
    "enabled": true
  }
}

That's it. The rule discovers a project-local .config/.ignition-pylintrc if one exists, otherwise it falls back to the bundled package config, and runs every script through pylint with the default category mapping.

Common configurations​

Strict — every finding fails the build​

For projects that want CI to fail on style violations too, not just bugs:

{
  "PylintScriptRule": {
    "enabled": true,
    "kwargs": {
      "category_mapping": {
        "F": "error",
        "E": "error",
        "W": "error",
        "C": "error",
        "R": "error"
      }
    }
  }
}

Permissive — only fatal errors fail​

For projects that are still cleaning up legacy scripts and only want the build to fail on unparseable code:

{
  "PylintScriptRule": {
    "enabled": true,
    "kwargs": {
      "category_mapping": {
        "F": "error",
        "E": "warning",
        "W": "warning",
        "C": "warning",
        "R": "warning"
      }
    }
  }
}

Custom pylintrc path​

For projects that keep their pylint config somewhere non-standard:

{
  "PylintScriptRule": {
    "enabled": true,
    "kwargs": {
      "pylintrc": "ci/pylint/perspective.pylintrc"
    }
  }
}

Relative paths are resolved against the current working directory.

Batch mode for faster CI​

When linting many views at once, batch mode runs pylint a single time across all scripts instead of once per file:

{
  "PylintScriptRule": {
    "enabled": true,
    "kwargs": {
      "batch_mode": true
    }
  }
}

Trade-off: batch mode disables trailing-whitespace auto-fix and prints fully qualified script paths (<file>::<script>) in violation output.

What it lints​

The rule submits four script categories to pylint:

  • Event handler scripts — onActionPerformed, onClick, and every other events.* script
  • Message handler scripts — entries under scripts.messageHandlers
  • Custom component methods — entries under scripts.customMethods
  • Transform scripts — script transforms attached to property bindings

For the precise JSON path each node type maps to, see the reference's script types table.

Examples​

Correct code​

A clean event handler from tests/cases/AllScriptTypes/view.json passes pylint under the default configuration:

{
  "events": {
    "component": {
      "onActionPerformed": {
        "config": {
          "script": "\tsystem.perspective.print('ActionButton Pressed')"
        },
        "scope": "G",
        "type": "script"
      }
    }
  }
}

The script is tab-indented (required so the source is valid Python after the wrapping function header), uses the stubbed system global, and has no unresolved references.

Problematic code​

A real event handler from tests/cases/PylintViolations/view.json triggers four different pylint categories at once:

{
  "events": {
    "component": {
      "onActionPerformed": {
        "config": {
          "script": "\timport json\n\timport sys\n\tprint(undefined_variable)\n\tresult = some_object.nonexistent_method()"
        },
        "scope": "G",
        "type": "script"
      }
    }
  }
}

This single script produces:

  • W0611 — unused import json and unused import sys (warnings)
  • E0602 — undefined variable undefined_variable (error)
  • E1101 — instance has no nonexistent_method member (error)

Output format​

Findings are grouped by pylint category and routed to the errors or warnings stream according to category_mapping. A typical mixed output:

    Pylint - Error (E):
      • root.SubmitButton.onActionPerformed: Line 3: Undefined variable 'undefined_variable' (E0602)

    Pylint - Warning (W):
      • root.SubmitButton.onActionPerformed: Line 1: Unused import json (W0611)

Categories always render in F, E, W, C, R order regardless of how pylint emits them, and empty categories are omitted.

What --fix does​

When run with --fix, the rule strips trailing whitespace from any script that has a C0303 violation. The fix rewrites the script body once (one SET_VALUE per affected script, not per line) and is marked safe, so it is applied by default.

No other pylint finding has an auto-fix. "Remove unused import", "rename invalid variable", and "add missing docstring" all require more context than the rule can safely infer, so those are reported as violations only.

Trailing-whitespace fixes are also disabled in batch_mode — see the reference for the full rationale.

Pylintrc​

If pylintrc is not set, the rule searches for .config/.ignition-pylintrc starting from the current working directory and walking upward to the filesystem root. The closest match wins. If nothing is found in the project tree, it falls back to the .config/.ignition-pylintrc shipped inside the installed ignition_lint package. If that's also missing, it falls back to a small inline ruleset: unused-import, undefined-variable, syntax-error, invalid-name.

For the full lookup sequence (including how absolute and relative pylintrc paths are handled, what happens when the file is missing, and how the bundled config is located), see the reference's pylintrc resolution order.

Common gotchas​

  • Scripts must be indented. Perspective stores script bodies as plain strings that the rule wraps inside a function header, so the body must start with leading tabs or spaces. Unindented scripts are flagged as a data-quality issue separate from any pylint finding.
  • Don't mix tabs and spaces. Indentation that contains both tabs and spaces on the same line is flagged with Script mixes tabs and spaces for indentation. Use either tabs OR spaces consistently. Pick one style per script.
  • Ignition built-ins are stubbed. The combined temp file injects system = None, self = {}, and event = {} at the top, so referencing those names does not trigger undefined-variable (E0602). Anything else pylint cannot resolve is reported normally.
  • Function-redefined is suppressed. Multiple custom methods can define the same helper name (e.g. two methods that both define a _validate helper). The bundling concatenates them, which would otherwise trip pylint's function-redefined check, so it's disabled.
  • Empty scripts are skipped. If a script contains only whitespace, pylint is not invoked for it at all.

See also​