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String destructuring #1430

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2 changes: 2 additions & 0 deletions src/transformation/visitors/binary-expression/assignments.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -225,6 +225,8 @@ export function transformAssignmentStatement(

if (ts.isArrayLiteralExpression(expression.right)) {
right = transformExpressionList(context, expression.right.elements);
} else if (ts.isStringLiteral(expression.right)) {
right = Array.from(expression.right.text).map(c => lua.createStringLiteral(c));
} else {
right = context.transformExpression(expression.right);
if (!isMultiReturnCall(context, expression.right) && isArrayType(context, rightType)) {
Expand Down
106 changes: 78 additions & 28 deletions src/transformation/visitors/variable-declaration.ts
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Expand Up @@ -13,6 +13,7 @@ import { transformIdentifier } from "./identifier";
import { isMultiReturnCall } from "./language-extensions/multi";
import { transformPropertyName } from "./literal";
import { moveToPrecedingTemp } from "./expression-list";
import { isStringType } from "../utils/typescript";

export function transformArrayBindingElement(
context: TransformationContext,
Expand Down Expand Up @@ -40,7 +41,8 @@ export function transformBindingPattern(
context: TransformationContext,
pattern: ts.BindingPattern,
table: lua.Expression,
propertyAccessStack: ts.PropertyName[] = []
propertyAccessStack: ts.PropertyName[] = [],
isStringBinding = false
): lua.Statement[] {
const result: lua.Statement[] = [];

Expand Down Expand Up @@ -125,10 +127,21 @@ export function transformBindingPattern(
);
}
} else {
expression = lua.createTableIndexExpression(
tableExpression,
ts.isObjectBindingPattern(pattern) ? propertyName : lua.createNumericLiteral(index + 1)
);
if (isStringBinding) {
// don't add 1 to index stringaccess already takes care of that
expression = transformLuaLibFunction(
context,
LuaLibFeature.StringAccess,
pattern,
table,
lua.createNumericLiteral(index)
);
} else {
expression = lua.createTableIndexExpression(
tableExpression,
ts.isObjectBindingPattern(pattern) ? propertyName : lua.createNumericLiteral(index + 1)
);
}
}

result.push(...createLocalOrExportedOrGlobalDeclaration(context, variableName, expression));
Expand All @@ -153,36 +166,67 @@ export function transformBindingPattern(
return result;
}

export function transformBindingVariableDeclaration(
function requiresComplexBindingVariableDeclaration(
context: TransformationContext,
bindingPattern: ts.BindingPattern,
initializer?: ts.Expression
): lua.Statement[] {
const statements: lua.Statement[] = [];

// For object, nested or rest bindings fall back to transformBindingPattern
): boolean {
// For object, strings, nested or rest bindings fall back to transformBindingPattern
const isComplexBindingElement = (e: ts.ArrayBindingElement) =>
ts.isBindingElement(e) && (!ts.isIdentifier(e.name) || e.dotDotDotToken);

if (ts.isObjectBindingPattern(bindingPattern) || bindingPattern.elements.some(isComplexBindingElement)) {
let table: lua.Expression;
if (initializer) {
// Contain the expression in a temporary variable
let expression = context.transformExpression(initializer);
if (isMultiReturnCall(context, initializer)) {
expression = wrapInTable(expression);
}
const { precedingStatements: moveStatements, result: movedExpr } = transformInPrecedingStatementScope(
context,
() => moveToPrecedingTemp(context, expression, initializer)
);
statements.push(...moveStatements);
table = movedExpr;
} else {
table = lua.createAnonymousIdentifier();
const hasStringInitializer = initializer && isStringType(context, context.checker.getTypeAtLocation(initializer));

return (
ts.isObjectBindingPattern(bindingPattern) ||
bindingPattern.elements.some(isComplexBindingElement) ||
Boolean(hasStringInitializer)
);
}
function transformComplexBindingVariableDeclaration(
context: TransformationContext,
bindingPattern: ts.BindingPattern,
initializer?: ts.Expression
): lua.Statement[] {
const statements: lua.Statement[] = [];

let table: lua.Expression;
if (initializer) {
// Contain the expression in a temporary variable
let expression = context.transformExpression(initializer);
if (isMultiReturnCall(context, initializer)) {
expression = wrapInTable(expression);
}
statements.push(...transformBindingPattern(context, bindingPattern, table));
return statements;
const { precedingStatements: moveStatements, result: movedExpr } = transformInPrecedingStatementScope(
context,
() => moveToPrecedingTemp(context, expression, initializer)
);
statements.push(...moveStatements);
table = movedExpr;
} else {
table = lua.createAnonymousIdentifier();
}
statements.push(
...transformBindingPattern(
context,
bindingPattern,
table,
[],
initializer && isStringType(context, context.checker.getTypeAtLocation(initializer))
)
);
return statements;
}

export function transformBindingVariableDeclaration(
context: TransformationContext,
bindingPattern: ts.BindingPattern,
initializer?: ts.Expression
): lua.Statement[] {
const statements: lua.Statement[] = [];

if (requiresComplexBindingVariableDeclaration(context, bindingPattern, initializer)) {
return transformComplexBindingVariableDeclaration(context, bindingPattern, initializer);
}

const vars =
Expand All @@ -208,6 +252,12 @@ export function transformBindingVariableDeclaration(
? initializer.elements.map(e => context.transformExpression(e))
: lua.createNilLiteral();
statements.push(...createLocalOrExportedOrGlobalDeclaration(context, vars, values, initializer));
} else if (ts.isStringLiteral(initializer)) {
const values =
initializer.text.length > 0
? Array.from(initializer.text).map(c => lua.createStringLiteral(c))
: lua.createNilLiteral();
statements.push(...createLocalOrExportedOrGlobalDeclaration(context, vars, values, initializer));
} else {
// local vars = this.transpileDestructingAssignmentValue(node.initializer);
const unpackedInitializer = createUnpackCall(
Expand Down
41 changes: 41 additions & 0 deletions test/unit/destructuring.spec.ts
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Expand Up @@ -237,3 +237,44 @@ test("no exception from semantically invalid TS", () => {
.disableSemanticCheck()
.expectToHaveDiagnostics([invalidMultiReturnAccess.code, cannotAssignToNodeOfKind.code]);
});

describe("string destructuring", () => {
test("string literal declaration", () => {
util.testFunction`
const [a, b, c] = "test";
return { a, b, c };
`.expectToMatchJsResult();
});

test("string literal assignment", () => {
util.testFunction`
let a = "";
let b = "";
let c = "";
[a, b, c] = "test";
return { a, b, c };
`
.debug()
.expectToMatchJsResult();
});

test("string assignment", () => {
util.testFunction`
const foo = "test";
const [a, b, c] = foo;
return { a, b, c };
`.expectToMatchJsResult();
});

// not wokring right now: send help pls
test("for loop init", () => {
util.testFunction`
const foo = "test";
for (const [a, b, c] of foo) {
return { a, b, c };
}
`
.debug()
.expectToMatchJsResult();
});
});