Improve and test remappings parsing logic

packages/hardhat-foundry/src/foundry.ts

@@ -31,24 +31,39 @@ export function getForgeConfig() {
   return JSON.parse(runCmdSync("forge config --json"));
 }
 
-export async function getRemappings() {
-  // Get remappings only once
-  if (cachedRemappings === undefined) {
-    cachedRemappings = runCmd("forge remappings").then((remappingsTxt) => {
-      const remappings: Remappings = {};
-      const remappingLines = remappingsTxt.split(/\r\n|\r|\n/);
-      for (const remappingLine of remappingLines) {
-        const fromTo = remappingLine.split("=");
+export function parseRemappings(remappingsTxt: string): Remappings {
+  const remappings: Remappings = {};
+  const remappingLines = remappingsTxt.split(/\r\n|\r|\n/);
+  for (const remappingLine of remappingLines) {
+    if (remappingLine.includes(":")) {
+      throw new HardhatFoundryError(
+        `Invalid remapping '${remappingLine}', remapping contexts are not allowed`
+      );
+    }
 
-        if (fromTo.length !== 2 || fromTo[0].includes(":")) {
-          continue;
-        }
+    if (!remappingLine.includes("=")) {
+      throw new HardhatFoundryError(
+        `Invalid remapping '${remappingLine}', remappings without a target are not allowed`
+      );
+    }
+
+    const fromTo = remappingLine.split("=");
 
-        remappings[fromTo[0]] = fromTo[1];
-      }
+    // if the remapping already exists, we ignore it because the first one wins
+    if (remappings[fromTo[0]] !== undefined) {
+      continue;
+    }
 
-      return remappings;
-    });
+    remappings[fromTo[0]] = fromTo[1];
+  }
+
+  return remappings;
+}
+
+export async function getRemappings() {
+  // Get remappings only once
+  if (cachedRemappings === undefined) {
+    cachedRemappings = runCmd("forge remappings").then(parseRemappings);
   }
 
   return cachedRemappings;

packages/hardhat-foundry/test/foundry.ts

@@ -0,0 +1,36 @@
+import { expect } from "chai";
+import { HardhatFoundryError, parseRemappings } from "../src/foundry";
+
+describe("foundry module", function () {
+  describe("parseRemappings", function () {
+    it("should parse simple remappings", async function () {
+      const remappings = parseRemappings("a=b\nb=c\nc=d");
+
+      expect(remappings).to.deep.equal({
+        a: "b",
+        b: "c",
+        c: "d",
+      });
+    });
+
+    it("should throw if a remapping has a context", async function () {
+      expect(() => parseRemappings("a:b=c")).to.throw(
+        "Invalid remapping 'a:b=c', remapping contexts are not allowed"
+      );
+    });
+
+    it("should throw if a remapping doesn't have a target", async function () {
+      expect(() => parseRemappings("a")).to.throw(
+        "Invalid remapping 'a', remappings without a target are not allowed"
+      );
+    });
+
+    it("should use the first remapping if more than one has the same prefix", async function () {
+      const remappings = parseRemappings("a=b\na=c");
+
+      expect(remappings).to.deep.equal({
+        a: "b",
+      });
+    });
+  });
+});