Defensive Programming

Kind: principle

Layer: Correctness Core

Record: architecture:defensive-programming

Severity: mandatory

Scope: function, module, boundary

Canonical: Ontology

A design rule that code checks its inputs and assumptions before acting on them, and reports a violation as an explicit error.

Listed in Architecture principles, after Competing Consumers and before Fail Fast.

Requires

• Input Validation
• Error Handling

Reinforces

• Robustness
• Fail Fast

Enables

• Safe Failure

Conflicts with

• Trusting Invalid Inputs

In tension with

• Verbosity

Tensions

• Defensive Programming / Verbosity

Violated by

• Trusting Invalid Inputs

Refactored by

• Precondition Check
• Input Validation

Severity

• mandatory

Category

• Error Handling / Resilience

Linked from

• Execution joins the halves
• Error Handling / Resilience
• Security / Privacy / Compliance / Governance
• Correctness / Determinism / Verification
• Error Handling / Resilience
• Quality Attributes
• Severity levels
• The resolutions