Timothy J. Aveni
55 lines
2.2 KiB
TypeScript
55 lines
2.2 KiB
TypeScript
import { parse } from "@babel/parser";
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type Node = { type: string; start: number; end: number; [key: string]: unknown };
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const node = (value: unknown): value is Node =>
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!!value && typeof value === "object" && typeof (value as Node).type === "string";
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/** One requested insertion into ordinary authored TypeScript, not regeneration.
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* Ambiguous/custom wiring is left alone with an actionable error. */
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export function addImplementation(
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text: string,
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factory: "createRuntime" | "serveMigration",
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key: string,
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importPath: string,
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migrationOnly = false,
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): string {
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const ast = parse(text, { sourceType: "module", plugins: ["typescript"] });
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const objects: Node[] = [];
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const names = new Set<string>();
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const visit = (value: unknown) => {
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if (Array.isArray(value)) {
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value.forEach(visit);
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return;
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}
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if (!node(value)) return;
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if (value.type === "Identifier") names.add(String(value.name));
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if (
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value.type === "CallExpression" &&
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node(value.callee) &&
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value.callee.type === "Identifier" &&
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value.callee.name === factory &&
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Array.isArray(value.arguments) &&
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value.arguments.length === 1 &&
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node(value.arguments[0]) &&
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value.arguments[0].type === "ObjectExpression"
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)
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objects.push(value.arguments[0]);
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Object.values(value).forEach(visit);
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};
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visit(ast);
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if (objects.length !== 1)
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throw new Error(
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`Cannot safely add implementation: expected one ${factory}({...}) literal. Wire the handler in your authored server code instead.`,
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);
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const object = objects[0];
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if (
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(object.properties as Node[]).some((p) => node(p.key) && !p.computed && (p.key.name === key || p.key.value === key))
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)
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throw new Error(`Implementation already exists for ${key}`);
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let alias = "qxImplementation";
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for (let index = 1; names.has(alias); index++) alias = `qxImplementation${index}`;
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const value = migrationOnly ? 'async () => { throw new Error("Migration-only export"); }' : alias;
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const insertion = object.start + 1;
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const edited = text.slice(0, insertion) + `\n ${JSON.stringify(key)}: ${value},\n` + text.slice(insertion);
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return (migrationOnly ? "" : `import {handler as ${alias}} from ${JSON.stringify(importPath)};\n`) + edited;
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}
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