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Fix custom sidebar function return and file-scope bindings #9501

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Fix custom sidebar function return and file-scope bindings #9501

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ca520f1
test: cover sidebar function scope and return semantics
austinywang Aug 4, 2026
7b168f0
Fix sidebar function return and root scope semantics
austinywang Aug 4, 2026
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94 changes: 73 additions & 21 deletions Packages/macOS/CmuxSwiftRender/Sources/CmuxSwiftRender/SwiftViewInterpreter.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,7 @@ public struct SwiftViewInterpreter: Sendable {
onLargeStack {
let env = EvalEnvironment(values: state)
self.registerFunctions(program.file.statements, env)
self.bindTopLevelVariables(program.file.statements, env)
for item in program.file.statements {
if let expr = item.item.as(ExprSyntax.self), let node = self.evalView(expr, env) {
// A tripped node budget means the tree was truncated
Expand Down Expand Up @@ -114,6 +115,16 @@ public struct SwiftViewInterpreter: Sendable {
}
}

/// Binds file-scope variables into the root environment so user functions
/// can resolve constants declared outside their bodies.
private func bindTopLevelVariables(_ items: CodeBlockItemListSyntax, _ env: EvalEnvironment) {
for item in items {
if let decl = item.item.as(VariableDeclSyntax.self) {
applyBinding(decl, env)
}
}
}

private func bindParameters(_ decl: FunctionDeclSyntax, _ call: FunctionCallExprSyntax, _ env: EvalEnvironment) -> EvalEnvironment {
expressions.bindParameters(decl, call, env)
}
Expand Down Expand Up @@ -296,7 +307,7 @@ public struct SwiftViewInterpreter: Sendable {
// called in view position; evaluate its body as view items.
if let decl = env.lookupFunction(ref.baseName.text), let body = decl.body {
let scope = bindParameters(decl, call, env)
let nodes = evalItems(body.statements, scope)
let nodes = evalItemsResult(body.statements, scope).nodes
if nodes.count == 1 { return nodes[0] }
return RenderNode(kind: .vstack, children: nodes)
}
Expand All @@ -306,10 +317,28 @@ public struct SwiftViewInterpreter: Sendable {

// MARK: - ViewBuilder statements

/// The rendered nodes from a block and whether an explicit `return`
/// terminated the current function evaluation.
private enum ViewBlockResult {
case completed([RenderNode])
case returned([RenderNode])

var nodes: [RenderNode] {
switch self {
case let .completed(nodes), let .returned(nodes):
nodes
}
}
}

private func evalItems(_ items: CodeBlockItemListSyntax, _ env: EvalEnvironment) -> [RenderNode] {
evalItemsResult(items, env).nodes
}

private func evalItemsResult(_ items: CodeBlockItemListSyntax, _ env: EvalEnvironment) -> ViewBlockResult {
env.budget.enter()
defer { env.budget.leave() }
guard !env.budget.exceeded, !env.budget.nodesExceeded else { return [] }
guard !env.budget.exceeded, !env.budget.nodesExceeded else { return .completed([]) }
registerFunctions(items, env)
var out: [RenderNode] = []
for item in items {
Expand All @@ -320,21 +349,39 @@ public struct SwiftViewInterpreter: Sendable {
if let decl = node.as(VariableDeclSyntax.self) {
applyBinding(decl, env)
} else if let loop = node.as(ForStmtSyntax.self) {
out += evalFor(loop, env)
switch evalFor(loop, env) {
case let .completed(nodes):
out += nodes
case let .returned(nodes):
return .returned(nodes)
}
} else if let ifExpr = ifExpression(node) {
out += evalIf(ifExpr, env)
switch evalIf(ifExpr, env) {
case let .completed(nodes):
out += nodes
case let .returned(nodes):
return .returned(nodes)
}
} else if let switchExpr = switchExpression(node) {
out += evalSwitch(switchExpr, env)
switch evalSwitch(switchExpr, env) {
case let .completed(nodes):
out += nodes
case let .returned(nodes):
return .returned(nodes)
}
} else if let ret = node.as(ReturnStmtSyntax.self), let expr = ret.expression {
// A view helper with an explicit `return SomeView` (or
// `return ForEach(...) { }`) renders its returned expression,
// not nothing.
// not nothing, and exits the function instead of appending to
// the surrounding builder output.
var returned: [RenderNode] = []
if let call = expr.as(FunctionCallExprSyntax.self), isForEach(call) {
out += evalForEach(call, env)
returned = evalForEach(call, env)
} else if let child = evalView(expr, env) {
env.budget.recordNode()
out.append(child)
returned = [child]
}
return .returned(returned)
} else if let expr = node.as(ExprSyntax.self) {
if let call = expr.as(FunctionCallExprSyntax.self), isForEach(call) {
out += evalForEach(call, env)
Expand All @@ -344,7 +391,7 @@ public struct SwiftViewInterpreter: Sendable {
}
}
}
return out
return .completed(out)
}

/// Extracts an `if` from a code-block item, whether it appears directly
Expand Down Expand Up @@ -530,15 +577,15 @@ public struct SwiftViewInterpreter: Sendable {

/// Evaluates a view-position `switch`: the first matching (or `default`)
/// case's statements are rendered.
private func evalSwitch(_ switchExpr: SwitchExprSyntax, _ env: EvalEnvironment) -> [RenderNode] {
private func evalSwitch(_ switchExpr: SwitchExprSyntax, _ env: EvalEnvironment) -> ViewBlockResult {
let subject = expressions.eval(switchExpr.subject, env)
for caseSyntax in switchExpr.cases {
guard let switchCase = caseSyntax.as(SwitchCaseSyntax.self) else { continue }
if switchCaseMatches(switchCase.label, subject, env) {
return evalItems(switchCase.statements, env.makeChild())
return evalItemsResult(switchCase.statements, env.makeChild())
}
}
return []
return .completed([])
}

/// Whether a `switch` case label matches `subject` (literal/`.member`
Expand All @@ -561,35 +608,40 @@ public struct SwiftViewInterpreter: Sendable {
}
}

private func evalFor(_ loop: ForStmtSyntax, _ env: EvalEnvironment) -> [RenderNode] {
private func evalFor(_ loop: ForStmtSyntax, _ env: EvalEnvironment) -> ViewBlockResult {
guard let name = loop.pattern.as(IdentifierPatternSyntax.self)?.identifier.text,
let sequence = expressions.eval(loop.sequence, env),
let values = sequence.iterationValues else { return [] }
let values = sequence.iterationValues else { return .completed([]) }
var out: [RenderNode] = []
for value in values {
if env.budget.nodesExceeded { break } // same early-out as evalForEach
let scope = env.makeChild()
scope.define(name, value)
out += evalItems(loop.body.statements, scope)
switch evalItemsResult(loop.body.statements, scope) {
case let .completed(nodes):
out += nodes
case let .returned(nodes):
return .returned(nodes)
}
}
return out
return .completed(out)
}

private func evalIf(_ ifExpr: IfExprSyntax, _ env: EvalEnvironment) -> [RenderNode] {
private func evalIf(_ ifExpr: IfExprSyntax, _ env: EvalEnvironment) -> ViewBlockResult {
// The then-branch runs in a child scope so `if let x = …` bindings are
// visible to it.
let scope = env.makeChild()
if conditionsPass(ifExpr.conditions, scope) {
return evalItems(ifExpr.body.statements, scope)
return evalItemsResult(ifExpr.body.statements, scope)
}
guard let elseBody = ifExpr.elseBody else { return [] }
guard let elseBody = ifExpr.elseBody else { return .completed([]) }
if let block = elseBody.as(CodeBlockSyntax.self) {
return evalItems(block.statements, env.makeChild())
return evalItemsResult(block.statements, env.makeChild())
}
if let elseIf = elseBody.as(IfExprSyntax.self) {
return evalIf(elseIf, env)
}
return []
return .completed([])
}

/// Evaluates an `if`/`guard` condition list against `scope`, binding any
Expand Down
26 changes: 26 additions & 0 deletions Packages/macOS/CmuxSwiftRender/Tests/CmuxSwiftRenderTests/SwiftViewInterpreterTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -319,6 +319,32 @@ import Testing
#expect(node?.children.first?.children.first?.text == "one")
}

@Test func returnExitsViewFunctionBeforeFallthrough() {
let node = interp.evaluate("""
func badge(_ w) -> some View {
if w.unread == 0 { return AnyView(Text("EARLY")) }
return AnyView(Text("FALLTHROUGH"))
}
VStack { badge(w) }
""", state: [
"w": .object(["unread": .int(0)]),
])
#expect(node?.kind == .vstack)
#expect(node?.children.map(\.text) == ["EARLY"])
}

@Test func topLevelLetIsVisibleInsideFunction() {
let node = interp.evaluate("""
let MARK = "X:"
func label(_ v) -> String { return "\\(MARK)\\(v)" }
VStack { Text(label(s)) }
""", state: [
"s": .string("a-b-c"),
])
#expect(node?.kind == .vstack)
#expect(node?.children.map(\.text) == ["X:a-b-c"])
}

@Test func numberFormattedCurrencyAndReduce() {
let items = SwiftValue.array([
.object(["cost": .double(1.5)]),
Expand Down
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