If/Else Conditionals

If/else conditionals let you include or exclude blocks, attributes, and children based on boolean expressions. Like for loops, they are declarative: the conditional is fully resolved during the control flow expansion phase, and only the matching branch appears in the evaluated document.

Syntax

if expression {
  // branch body
} else if expression {
  // branch body
} else {
  // fallback body
}

Any number of else if clauses may be chained. The else clause is optional. All branches are syntactically identical to block bodies and can contain any WCL statements.

Conditions Must Be Boolean

WCL does not perform implicit coercion on condition expressions. The expression must evaluate to a bool. Passing a non-bool value is a compile-time error:

let count = 5

// Correct
if count > 0 { ... }

// Error: count is an int, not a bool
if count { ... }

Conditionals Inside Block Bodies

The most common use of if/else is to selectively include attributes or child blocks inside a block body:

service api {
  port: 8080

  if env == "prod" {
    replicas: 3
    tls: true
  } else {
    replicas: 1
    tls: false
  }
}

Inline Attribute Values

if/else can appear as an expression to select between two values:

service api {
  replicas: if env == "prod" { 3 } else { 1 }
  log_level: if debug { "debug" } else { "info" }
}

When used as an expression, each branch must contain exactly one value expression.

Using Queries as Conditions

The result of has() or a boolean query expression can drive a conditional:

for svc in query(service) {
  if has(svc, "port") {
    ingress ingress-${svc.name} {
      target: svc.name
      port: svc.port
    }
  }
}

if has_decorator(myblock, "public") {
  expose myblock {
    external: true
  }
}

Chained Conditions

let tier = "gold"

config limits {
  max_requests: if tier == "gold" {
    10000
  } else if tier == "silver" {
    5000
  } else {
    1000
  }
}

Composition with For Loops

if/else and for loops compose freely. A conditional can appear inside a for loop body, and a for loop can appear inside a conditional branch:

for env in ["staging", "prod"] {
  service web-${env} {
    replicas: if env == "prod" { 3 } else { 1 }

    if env == "prod" {
      alerts {
        pagerduty: true
      }
    }
  }
}

if enable_workers {
  for i in range(0, worker_count) {
    worker worker-${i} {
      id: i
    }
  }
}

Discarded Branches Are Not Validated

Only the matching branch is included in the expanded AST. The other branches are discarded before evaluation and schema validation. This means a discarded branch can reference names or produce structures that would otherwise be invalid, as long as the condition that guards it is false:

if false {
  // This block is never evaluated, so undefined_var is not an error
  item x { value: undefined_var }
}

Use this carefully — relying on discarded branches to suppress errors can make configs harder to understand.

Nesting Depth

If/else conditionals count toward the global nesting depth limit (default 32), shared with for loops.

Expansion Phase

Conditionals are expanded during phase 5: control flow expansion, after macro expansion. At the end of this phase the AST contains only the winning branch’s content and no if/else nodes remain.