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Reduce cognitive complexity
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@jg-rp
jg-rp committed Aug 3, 2024
1 parent 9002214 commit a72c46f
Showing 1 changed file with 88 additions and 95 deletions.
183 changes: 88 additions & 95 deletions src/path/parse.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -538,16 +538,11 @@ export class Parser {
);
}

// eslint-disable-next-line sonarjs/cognitive-complexity
protected unescapeString(value: string, token: Token): string {
const rv: string[] = [];
const length = value.length;
let index = 0;
let digits: string;
let codepoint: number;
let lowSurrogate: number;
let unescaped: string;
let codepointAt: number | undefined;

while (index < length) {
const ch = value[index];
Expand Down Expand Up @@ -581,98 +576,14 @@ export class Parser {
rv.push("\t");
break;
case "u":
if (index + 4 >= length) {
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index}`,
token,
);
}

index += 1;

digits = value.slice(index, index + 4);
codepoint = this.parseInt16(digits, token);

if (isNaN(codepoint)) {
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index}`,
token,
);
}

if (
index + 5 < length &&
value[index + 4] === "\\" &&
value[index + 5] === "u"
) {
// expect a surrogate pair
if (index + 9 >= length || !isHighSurrogate(codepoint)) {
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index}`,
token,
);
}

digits = value.slice(index + 6, index + 10);
lowSurrogate = this.parseInt16(digits, token);

if (isNaN(lowSurrogate) || !isLowSurrogate(lowSurrogate)) {
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index + 4}`,
token,
);
}

codepoint =
0x10000 +
(((codepoint & 0x03ff) << 10) | (lowSurrogate & 0x03ff));

index += 6;
} else if (
isHighSurrogate(codepoint) ||
isLowSurrogate(codepoint)
) {
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index}`,
token,
);
}

try {
unescaped = String.fromCodePoint(codepoint);
} catch {
// TODO: offset is wrong
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index}`,
token,
);
}

codepointAt = unescaped.codePointAt(0);
if (codepointAt !== undefined && codepointAt <= 0x1f) {
throw new JSONPathSyntaxError(
`invalid character at offset ${index}`,
token,
);
}

rv.push(unescaped);
index += 3;
[codepoint, index] = this.decodeEscapeSequence(value, index, token);
rv.push(this.stringFromCodePoint(codepoint, token));
break;
default:
throw new JSONPathSyntaxError(
`invalid escape sequence at offset ${index}`,
token,
);
throw new JSONPathSyntaxError("invalid escape sequence", token);
}
} else {
codepointAt = ch.codePointAt(0);
if (codepointAt !== undefined && codepointAt <= 0x1f) {
throw new JSONPathSyntaxError(
`invalid character at offset ${index}`,
token,
);
}
this.stringFromCodePoint(ch.codePointAt(0), token);
rv.push(ch);
}

Expand All @@ -682,6 +593,72 @@ export class Parser {
return rv.join("");
}

/**
* Decode a `\uXXXX` or `\uXXXX\uXXXX` escape sequence from _value_ at _index_.
*
* @param value - A string value containing the sequence to decode.
* @param index - The start index of an escape sequence in _value_.
* @param token - The token for the string value.
* @returns - A codepoint, new index tuple.
*/
protected decodeEscapeSequence(
value: string,
index: number,
token: Token,
): [number, number] {
const length = value.length;

if (index + 4 >= length) {
throw new JSONPathSyntaxError("invalid escape sequence", token);
}

index += 1; // Move past 'u'
let codepoint = this.parseInt16(value.slice(index, index + 4), token);

if (isLowSurrogate(codepoint)) {
throw new JSONPathSyntaxError("invalid escape sequence", token);
}

if (isHighSurrogate(codepoint)) {
// Expect a surrogate pair.
if (
!(
index + 9 < length &&
value[index + 4] === "\\" &&
value[index + 5] === "u"
)
) {
throw new JSONPathSyntaxError("invalid escape sequence", token);
}

const lowSurrogate = this.parseInt16(
value.slice(index + 6, index + 10),
token,
);

if (!isLowSurrogate(lowSurrogate)) {
throw new JSONPathSyntaxError("invalid escape sequence", token);
}

codepoint =
0x10000 + (((codepoint & 0x03ff) << 10) | (lowSurrogate & 0x03ff));

return [codepoint, index + 9];
}

return [codepoint, index + 3];
}

/**
* Parse a hexadecimal string as an integer.
*
* @param digits - Hexadecimal digit string.
* @param token - The token for the string value.
* @returns - The number representation of _digits_.
*
* Note that we're not using `parseInt(digits, 16)` because it accepts `+`
* and `-` and things we don't allow.
*/
protected parseInt16(digits: string, token: Token): number {
const encoder = new TextEncoder();
let codepoint = 0;
Expand Down Expand Up @@ -726,6 +703,22 @@ export class Parser {
return codepoint;
}

/** Check the codepoint is valid and return its string representation. */
protected stringFromCodePoint(
codepoint: number | undefined,
token: Token,
): string {
if (codepoint === undefined || codepoint <= 0x1f) {
throw new JSONPathSyntaxError(`invalid character`, token);
}

try {
return String.fromCodePoint(codepoint);
} catch {
throw new JSONPathSyntaxError("invalid escape sequence", token);
}
}

protected throwForNonComparable(expr: FilterExpression): void {
if (
(expr instanceof RootQuery || expr instanceof RelativeQuery) &&
Expand Down Expand Up @@ -758,10 +751,10 @@ export class Parser {
}
}

function isHighSurrogate(codepoint: number): boolean {
export function isHighSurrogate(codepoint: number): boolean {
return codepoint >= 0xd800 && codepoint <= 0xdbff;
}

function isLowSurrogate(codepoint: number): boolean {
export function isLowSurrogate(codepoint: number): boolean {
return codepoint >= 0xdc00 && codepoint <= 0xdfff;
}

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