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Fix preceding statements with ternary operator #1234

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Merged
Perryvw merged 1 commit into from
Mar 17, 2022
Merged

Fix preceding statements with ternary operator #1234

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48 changes: 30 additions & 18 deletions src/transformation/visitors/conditional.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,28 +6,30 @@ import { performHoisting, popScope, pushScope, ScopeType } from "../utils/scope"
import { transformBlockOrStatement } from "./block";
import { canBeFalsy } from "../utils/typescript";

type EvaluatedExpression = [precedingStatemens: lua.Statement[], value: lua.Expression];

function transformProtectedConditionalExpression(
context: TransformationContext,
expression: ts.ConditionalExpression
expression: ts.ConditionalExpression,
condition: EvaluatedExpression,
whenTrue: EvaluatedExpression,
whenFalse: EvaluatedExpression
): lua.Expression {
const tempVar = context.createTempNameForNode(expression.condition);

const condition = context.transformExpression(expression.condition);

const [trueStatements, val1] = transformInPrecedingStatementScope(context, () =>
context.transformExpression(expression.whenTrue)
const trueStatements = whenTrue[0].concat(
lua.createAssignmentStatement(lua.cloneIdentifier(tempVar), whenTrue[1], expression.whenTrue)
);
trueStatements.push(lua.createAssignmentStatement(lua.cloneIdentifier(tempVar), val1, expression.whenTrue));

const [falseStatements, val2] = transformInPrecedingStatementScope(context, () =>
context.transformExpression(expression.whenFalse)
const falseStatements = whenFalse[0].concat(
lua.createAssignmentStatement(lua.cloneIdentifier(tempVar), whenFalse[1], expression.whenFalse)
);
falseStatements.push(lua.createAssignmentStatement(lua.cloneIdentifier(tempVar), val2, expression.whenFalse));

context.addPrecedingStatements([
lua.createVariableDeclarationStatement(tempVar, undefined, expression.condition),
...condition[0],
lua.createIfStatement(
condition,
condition[1],
lua.createBlock(trueStatements, expression.whenTrue),
lua.createBlock(falseStatements, expression.whenFalse),
expression
Expand All @@ -37,17 +39,27 @@ function transformProtectedConditionalExpression(
}

export const transformConditionalExpression: FunctionVisitor<ts.ConditionalExpression> = (expression, context) => {
if (canBeFalsy(context, context.checker.getTypeAtLocation(expression.whenTrue))) {
return transformProtectedConditionalExpression(context, expression);
const condition = transformInPrecedingStatementScope(context, () =>
context.transformExpression(expression.condition)
);
const whenTrue = transformInPrecedingStatementScope(context, () =>
context.transformExpression(expression.whenTrue)
);
const whenFalse = transformInPrecedingStatementScope(context, () =>
context.transformExpression(expression.whenFalse)
);
if (
whenTrue[0].length > 0 ||
whenFalse[0].length > 0 ||
canBeFalsy(context, context.checker.getTypeAtLocation(expression.whenTrue))
) {
return transformProtectedConditionalExpression(context, expression, condition, whenTrue, whenFalse);
}

const condition = context.transformExpression(expression.condition);
const val1 = context.transformExpression(expression.whenTrue);
const val2 = context.transformExpression(expression.whenFalse);

// condition and v1 or v2
const conditionAnd = lua.createBinaryExpression(condition, val1, lua.SyntaxKind.AndOperator);
return lua.createBinaryExpression(conditionAnd, val2, lua.SyntaxKind.OrOperator, expression);
context.addPrecedingStatements(condition[0]);
const conditionAnd = lua.createBinaryExpression(condition[1], whenTrue[1], lua.SyntaxKind.AndOperator);
return lua.createBinaryExpression(conditionAnd, whenFalse[1], lua.SyntaxKind.OrOperator, expression);
};

export function transformIfStatement(statement: ts.IfStatement, context: TransformationContext): lua.IfStatement {
Expand Down
26 changes: 26 additions & 0 deletions test/unit/conditionals.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -112,3 +112,29 @@ test.each([false, true, null])("Ternary conditional with generic whenTrue branch
})
.expectToMatchJsResult();
});

test.each([false, true])("Ternary conditional with preceding statements in true branch (%p)", trueVal => {
// language=TypeScript
util.testFunction`
let i = 0;
const result = ${trueVal} ? i += 1 : i;
return { result, i };
`
.setOptions({
strictNullChecks: true,
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@Perryvw Perryvw Mar 16, 2022

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Why is this option required here, I don't see any undefineds/nulls in the tests?

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@GlassBricks GlassBricks Mar 16, 2022 •
edited
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Without it, the test doesn't start as failing and detect the issue:
The type number with no strict null checks may be null and therefore falsy, so the if statement was used.

})
.expectToMatchJsResult();
});

test.each([false, true])("Ternary conditional with preceding statements in false branch (%p)", trueVal => {
// language=TypeScript
util.testFunction`
let i = 0;
const result = ${trueVal} ? i : i += 2;
return { result, i };
`
.setOptions({
strictNullChecks: true,
})
.expectToMatchJsResult();
});