bcquality/microsoft/knowledge/style/binary-choice-must-be-boolean.md
Michael Dieringer cc7c1f2ee0 Address Jesper Schulz-Wedde's review on PR #156
- Rename 3 articles so their .good.al/.bad.al companion stems match
  (do-not-change-primary-key, testfield-required-setup-field,
  al-identifiers-english), fixing the R14 orphan-sample errors.
- do-not-change-primary-key.good.al: include Flow in the new table's
  own primary key so it actually models the discriminating dimension.
- al-build-output-must-not-pollute-project-root.md: drop the
  unsubstantiated AL0197 causal claim and the non-existent
  al.outputPath setting; reframe as build-artifact hygiene sourced
  from ALTool --outfolder / al_build outputPath.
- prefer-email-module.md: Email Message is Codeunit 8904, not a table;
  distinguish it from the underlying Sent/Outbox/Draft storage.
- file-datatype-saas.md: File.Open/Create/Read/Write fails to compile
  against a Cloud-scoped project, it does not compile and silently
  fail at runtime.
- namespace-must-be-verified-from-source.md: narrow to "resolve from
  the referenced object's source or symbols," since source-file line
  one is not the only authoritative source (symbol packages, comments
  before the namespace line).
- test-data-must-be-random-and-complete.md: drop "assume an empty
  database" and "collision-free" absolutes; reframe around
  independence from unrelated business records and reserving explicit
  values for scenario-defining inputs.
- binary-choice-must-be-boolean.md: scope to genuine true/false
  semantics, not mechanical two-member-enum-to-boolean conversion.
- document-report-word-layout.md: scope down to a sourced Microsoft
  Learn recommendation instead of an unconditional performance
  guarantee; cite the three Learn pages.
- Wire the new articles into their review skills' candidate-selection
  signals (file-datatype-saas, prefer-email-module,
  namespace-must-be-verified-from-source, var-parameters-require-an-
  addressable-variable) so they can actually enter a worklist.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-21 22:25:26 +02:00

1.7 KiB

bc-version domain keywords technologies countries application-area
all
style
boolean
option
yes-no
magic-number
variable-typing
field-typing
al
w1
all

Binary yes/no choices must be typed as Boolean, not Option or Integer

Contributions welcome — open a PR to refine or extend this article.

Description

When a field or variable represents a genuine true/false state — yes/no, on/off, active/inactive, blocked/not blocked — it should be typed Boolean. Modeling that same predicate as an Option/Enum with two members, or as an Integer with two magic-number values, adds a layer of indirection a reader has to resolve before understanding the code. This is about semantics, not member count: a domain concept that currently has exactly two named alternatives — Inbound/Outbound, Debit/Credit, Buy/Sell — is not automatically a Boolean in disguise. An Enum can be the clearer model there, including when it needs to implement an interface, preserve an existing contract, or leave room for a future third value. The distinction is whether the domain is genuinely a stable predicate, not how many states it currently has.

Best Practice

Type a field or variable as Boolean when the domain concept is inherently a true/false state. Do not replace a meaningful two-option domain model with a Boolean solely because it currently has two values.

See sample: binary-choice-must-be-boolean.good.al.

Anti Pattern

Modeling a yes/no choice as an Option with two members, or as an Integer with magic-number values, forces every caller to remember which value means what and leaves room for a meaningless third value.

See sample: binary-choice-must-be-boolean.bad.al.