Implements pre-binding with restrictions on the CONSTRUCT query as de…

…fined by https://www.w3.org/TR/shacl/#pre-binding

src/lib/Generator.class.ts

@@ -28,9 +28,8 @@ export default class Generator {
  }
 
  public async loadStatements($this: NamedNode): Promise<ResultStream<Quad>> {
- // const values = this.query.values ?? []
- // values.push({$this})
- // this.query.values = values
+ // Prebinding, see https://www.w3.org/TR/shacl/#pre-binding
+ // we know the query is safe to use replacement since we checked it before
  const queryString = getSPARQLQueryString(this.query)
  .replaceAll(
  /[?$]\bthis\b/g,

src/utils/getSPARQLQuery.ts

@@ -1,31 +1,82 @@
-import chalk from 'chalk';
-import fs from 'fs'
-import { type SelectQuery, type ConstructQuery, Parser } from 'sparqljs'
+import chalk from "chalk";
+import fs from "fs";
+import {
+ type SelectQuery,
+ type ConstructQuery,
+ Parser,
+ type Pattern,
+} from "sparqljs";
 
-type QueryTypes = "select" | "construct"; 
+type QueryTypes = "select" | "construct";
 
-type QueryType<T> = 
- T extends "select" ? SelectQuery :
- T extends "construct" ? ConstructQuery :
- never;
+type QueryType<T> = T extends "select"
+ ? SelectQuery
+ : T extends "construct"
+ ? ConstructQuery
+ : never;
 
-export default function getSPARQLQuery<T extends QueryTypes>(queryStringOrFile: string, type: T): QueryType<T> {
- let query = ''
- if (queryStringOrFile.startsWith('file://')) {
- const file = queryStringOrFile.replace('file://', '')
+export default function getSPARQLQuery<T extends QueryTypes>(
+ queryStringOrFile: string,
+ type: T
+): QueryType<T> {
+ let query = "";
+ if (queryStringOrFile.startsWith("file://")) {
+ const file = queryStringOrFile.replace("file://", "");
  if (!fs.existsSync(file) || !fs.statSync(file).isFile()) {
  throw new Error(`File not found: ${chalk.italic(file)}`);
  }
- query = fs.readFileSync(file, 'utf-8')
+ query = fs.readFileSync(file, "utf-8");
  } else {
- query = queryStringOrFile
+ query = queryStringOrFile;
  }
- const parsed = (new Parser()).parse(query)
- if (parsed.type !== 'query') {
- throw new Error(`Unexpected querytype ${parsed.type}`)
+ const parsed = new Parser().parse(query);
+ if (parsed.type !== "query") {
+ throw new Error(`Unexpected querytype ${parsed.type}`);
+ }
+ if (parsed.queryType.toLowerCase() === type) {
+ const query = parsed as QueryType<T>;
+ if (query.queryType === "CONSTRUCT") {
+ checkSPARQLConstructQuery(query.where);
+ }
+ return query;
+ } else throw new Error(`Unexpected querytype ${parsed.queryType}`);
+}
+
+/**
+ * because we use prebinding, our query must follow the rules as specified by
+ * https://www.w3.org/TR/shacl/#pre-binding:
+ * - SPARQL queries must not contain a MINUS clause
+ * - SPARQL queries must not contain a federated query (SERVICE)
+ * - SPARQL queries must not contain a VALUES clause
+ * - SPARQL queries must not use the syntax form `AS ?var` for any potentially pre-bound variable
+ */
+function checkSPARQLConstructQuery(patterns?: Pattern[]): void {
+ if (patterns === undefined) return;
+ for (const pattern of patterns) {
+ if (pattern.type === 'bind') {
+ if(pattern.variable.value === 'this') {
+ throw new Error('SPARQL queries must not use the syntax form `AS ?this` because it is a pre-bound variable')
+ }
+ }
+ if (pattern.type === "minus")
+ throw new Error(
+ "SPARQL construct queries must not contain a MINUS clause"
+ );
+ if (pattern.type === "service")
+ throw new Error(
+ "SPARQL construct queries must not contain a SERVICE clause"
+ );
+ if (pattern.type === "values")
+ throw new Error(
+ "SPARQL construct queries must not contain a VALUES clause"
+ );
+ if (
+ pattern.type === "optional" ||
+ pattern.type === "union" ||
+ pattern.type === "group" ||
+ pattern.type === "graph"
+ ) {
+ checkSPARQLConstructQuery(pattern.patterns);
+ }
  }
- if (parsed.queryType.toLowerCase() === type)
- return parsed as QueryType<T>
- else 
- throw new Error(`Unexpected querytype ${parsed.queryType}`)
 }