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BSL020 — Control flow statements should not be nested too deep

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Summary

Control flow statements should not be nested too deep

Identifiers

Field Value
Rule code BSL020
Compatible alias NestedStatements
Severity WARNING
Enabled by default Yes
Implemented Yes
Tags brain-overload

Behavior

  • The public identifier BSL020 and alias NestedStatements are stable.
  • The rule reports the cases documented on this page.
  • Suppressions and project configuration are applied before publication.
  • The rule requires neither an external analyzer nor network access.

Configuration and suppression

BSL### is the primary stable identifier. The compatible alias is accepted in select, ignore, and compatible block suppression comments.

[tool.onec-hbk-bsl]
select = ["BSL020"]
ignore = ["NestedStatements"]

All three suppression families support both a current line and a range. When an opening comment follows code, it affects only that line. Use any one form:

  • noqa:
Value = "example";  // noqa: BSL020
  • bsl-disable:
Value = "example";  // bsl-disable: BSL020
  • compatible BSLLS form:
Value = "example";  // BSLLS:NestedStatements-off

When the same opening comment is on a line by itself, it starts a range. Close it with the matching marker from the same family:

// noqa: BSL020
// code without this diagnostic
// noqa-enable: BSL020

// bsl-disable: BSL020
// code without this diagnostic
// bsl-enable: BSL020

// BSLLS:NestedStatements-off
// code without this diagnostic
// BSLLS:NestedStatements-on

To disable the rule until the end of the file, omit the closing noqa-enable, bsl-enable, or BSLLS:…-on marker.

Opening and closing markers must belong to the same family.

Description

Nested "If, "For", "For Each", "While" and "Try" operators are the key ingredients for creating so-called "spaghetti code".

Such code is hard for reading, refactoring and support.

Examples

Incorrect

If Something Then                  // Allowed - level = 1
  /* ... */
  If Some Then             // Allowed - level = 2
    /* ... */
    For Num = 0 To 10 Do          // Allowed - level = 3
      /* ... */
      If OneMoreCondition Then     // Acceptable - level = 4, limit is reached, not yet breached
        If SomethingElse Then        // Level = 5, Limit is breached
          /* ... */
        EndIf;
        Return;
      EndIf;
    EndDo;
  EndIf;
EndIf;

Sources