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Fix side effects in string index causing issues #868

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Merged
Perryvw merged 2 commits into from
May 11, 2020
Merged

Fix side effects in string index causing issues #868

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5f5c58c
Fix side effects in string index causing issues
Perryvw May 9, 2020
52a6cb2
Removed unnecessary variable
Perryvw May 11, 2020
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46 changes: 36 additions & 10 deletions src/transformation/visitors/access.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ import { transformBuiltinPropertyAccessExpression } from "../builtins";
import { FunctionVisitor, TransformationContext } from "../context";
import { AnnotationKind, getTypeAnnotations } from "../utils/annotations";
import { createExpressionPlusOne } from "../utils/lua-ast";
import { isArrayType, isNumberType, isStringType } from "../utils/typescript";
import { isArrayType, isNumberType, isStringType, isExpressionWithEvaluationEffect } from "../utils/typescript";
import { tryGetConstEnumValue } from "./enum";
import { transformLuaTablePropertyAccessExpression, validateLuaTableElementAccessExpression } from "./lua-table";

Expand All @@ -31,20 +31,17 @@ export const transformElementAccessExpression: FunctionVisitor<ts.ElementAccessE
return constEnumValue;
}

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

const argumentType = context.checker.getTypeAtLocation(expression.argumentExpression);
const type = context.checker.getTypeAtLocation(expression.expression);
if (isNumberType(context, argumentType) && isStringType(context, type)) {
const index = context.transformExpression(expression.argumentExpression);
return lua.createCallExpression(
lua.createTableIndexExpression(lua.createIdentifier("string"), lua.createStringLiteral("sub")),
[table, createExpressionPlusOne(index), createExpressionPlusOne(index)],
expression
);
return transformStringIndex(context, expression);
}

return lua.createTableIndexExpression(table, transformElementAccessArgument(context, expression), expression);
return lua.createTableIndexExpression(
context.transformExpression(expression.expression),
transformElementAccessArgument(context, expression),
expression
);
};

export const transformPropertyAccessExpression: FunctionVisitor<ts.PropertyAccessExpression> = (
Expand Down Expand Up @@ -94,3 +91,32 @@ export const transformQualifiedName: FunctionVisitor<ts.QualifiedName> = (node,

return lua.createTableIndexExpression(left, right, node);
};

function transformStringIndex(context: TransformationContext, expression: ts.ElementAccessExpression): lua.Expression {
const string = context.transformExpression(expression.expression);
// Translate to string.sub(str, index, index), cache index in case it has side effects.
if (isExpressionWithEvaluationEffect(expression.argumentExpression)) {
const indexIdentifier = lua.createIdentifier("____index");
// string.sub(stringExpression, ____index, ____index)
const subCall = lua.createCallExpression(
lua.createTableIndexExpression(lua.createIdentifier("string"), lua.createStringLiteral("sub")),
[string, lua.cloneIdentifier(indexIdentifier), lua.cloneIdentifier(indexIdentifier)],
expression
);
// function(____index) string.sub(stringExpression, ____index, ____index)
const functionExpression = lua.createFunctionExpression(
lua.createBlock([lua.createReturnStatement([subCall])]),
[lua.cloneIdentifier(indexIdentifier)]
);
// (function(____index) string.sub(stringExpression, ____index, ____index) end)(index + 1)
const indexPlusOne = createExpressionPlusOne(context.transformExpression(expression.argumentExpression));
return lua.createCallExpression(functionExpression, [indexPlusOne]);
} else {
const index = context.transformExpression(expression.argumentExpression);
return lua.createCallExpression(
lua.createTableIndexExpression(lua.createIdentifier("string"), lua.createStringLiteral("sub")),
[string, createExpressionPlusOne(index), createExpressionPlusOne(index)],
expression
);
}
}
8 changes: 8 additions & 0 deletions test/unit/builtins/string.spec.ts
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Expand Up @@ -41,6 +41,14 @@ test.each([
util.testExpressionTemplate`${input}[${index}]`.expectToMatchJsResult();
});

test("string index with side effect", () => {
util.testFunction`
let i = 0;
const mystring = "abc";
return mystring[i++];
`.expectToMatchJsResult();
});

test.each([
{ inp: "hello test", searchValue: "", replaceValue: "" },
{ inp: "hello test", searchValue: " ", replaceValue: "" },
Expand Down