feat: add deduplication for interpolated fragment definitions in gql helper

Author: TDanks2000

src/__tests__/graphql.test.ts

@@ -101,6 +101,27 @@ describe("BaseHttpClient.graphql()", () => {
 		);
 	});
 
+	it("dedupes interpolated fragment definitions by fragment name", () => {
+		const fragment = gql`
+			fragment UserFields on User {
+				id
+				name
+			}
+		`;
+
+		const document = gql`
+			${fragment}
+			${fragment}
+			query GetUser {
+				user {
+					...UserFields
+				}
+			}
+		`;
+
+		expect(document.match(/fragment UserFields on User/g)).toHaveLength(1);
+	});
+
 	it("omits variables and operationName from the body when not provided", async () => {
 		let captured: RequestContext | undefined;
 

src/graphql/gql.ts

@@ -8,9 +8,78 @@ export function gql(
 	chunks: TemplateStringsArray,
 	...values: unknown[]
 ): string {
-	return chunks.reduce(
+	const source = chunks.reduce(
 		(source, chunk, index) =>
 			`${source}${chunk}${index in values ? String(values[index]) : ""}`,
 		"",
 	);
+
+	return dedupeFragmentDefinitions(source);
+}
+
+function dedupeFragmentDefinitions(source: string): string {
+	const seen = new Set<string>();
+	const fragmentPattern =
+		/\bfragment\s+([_A-Za-z][_0-9A-Za-z]*)\s+on\s+[_A-Za-z][_0-9A-Za-z]*/g;
+
+	let result = "";
+	let cursor = 0;
+	let match = fragmentPattern.exec(source);
+
+	while (match) {
+		const name = match[1];
+		if (!name) {
+			match = fragmentPattern.exec(source);
+			continue;
+		}
+
+		const bodyStart = source.indexOf("{", fragmentPattern.lastIndex);
+		if (bodyStart === -1) {
+			match = fragmentPattern.exec(source);
+			continue;
+		}
+
+		const bodyEnd = findMatchingBrace(source, bodyStart);
+		if (bodyEnd === -1) {
+			match = fragmentPattern.exec(source);
+			continue;
+		}
+
+		const fragmentStart = match.index;
+		const fragmentEnd = consumeTrailingWhitespace(source, bodyEnd + 1);
+
+		if (!seen.has(name)) {
+			seen.add(name);
+			result += source.slice(cursor, fragmentEnd);
+		} else {
+			result += source.slice(cursor, fragmentStart);
+		}
+
+		cursor = fragmentEnd;
+		fragmentPattern.lastIndex = fragmentEnd;
+		match = fragmentPattern.exec(source);
+	}
+
+	return result + source.slice(cursor);
+}
+
+function findMatchingBrace(source: string, openBraceIndex: number): number {
+	let depth = 0;
+
+	for (let index = openBraceIndex; index < source.length; index++) {
+		const char = source[index];
+		if (char === "{") depth++;
+		if (char === "}") depth--;
+		if (depth === 0) return index;
+	}
+
+	return -1;
+}
+
+function consumeTrailingWhitespace(source: string, index: number): number {
+	let next = index;
+	while (next < source.length && /\s/.test(source[next] ?? "")) {
+		next++;
+	}
+	return next;
 }