@parity/resolc fix sol file resolutions (#343)

second take on #339 

turns out that the resolve-pkg npm package was also failing to properly
resolve package with an exports field define in the package.json.

This fixes it and add a test case with such a package

js/resolc/src/index.test.ts

@@ -68,6 +68,16 @@ test('resolve import', () => {
       file: './fixtures/storage.sol',
       expected: resolve('fixtures/storage.sol'),
     },
+
+    // package with exports
+    {
+      file: '@redstone-finance/evm-connector/contracts/data-services/PrimaryProdDataServiceConsumerBase.sol',
+      expected: resolve(
+        __dirname,
+        '../../..',
+        'node_modules/@redstone-finance/evm-connector/contracts/data-services/PrimaryProdDataServiceConsumerBase.sol'
+      ),
+    },
     // scopped module with version
     {
       file: '@openzeppelin/contracts@5.1.0/token/ERC20/ERC20.sol',
@@ -100,16 +110,19 @@ test('resolve import', () => {
   ]
 
   for (const { file, expected } of cases) {
+    let resolved
     try {
-      const resolved = tryResolveImport(file)
-      assert(
-        resolved === expected,
-        `\nGot:\n${resolved}\nExpected:\n${expected}`
-      )
+      resolved = tryResolveImport(file)
     } catch (error) {
       assert(
         String(error) == expected,
-        `\nGot:\n${String(error)}\nExpected:\n${expected}`
+        `\nExpected:\n${expected}\nGot:\n${String(error)}\n`
+      )
+    }
+    if (resolved) {
+      assert(
+        resolved === expected,
+        `\nExpected:\n${expected}\nGot:\n${resolved}`
       )
     }
   }

js/resolc/src/index.ts

@@ -129,6 +129,26 @@ export async function compile(
   return resolc(input)
 }
 
+/**
+ * resolve the package root
+ * use resolve-pkg to find the package root, and fallback to using require.resolve if the package defines an exports field
+ * see https://github.com/sindresorhus/resolve-pkg/issues/9
+ **/
+function resolvePkgRoot(basePackage: string) {
+  const packageRoot = resolvePkg(basePackage)
+  if (packageRoot) {
+    return packageRoot
+  }
+
+  try {
+    const packageExport = require.resolve(basePackage)
+    const endIndex = packageExport.indexOf(basePackage) + basePackage.length
+    return packageExport.substring(0, endIndex)
+  } catch {}
+
+  return undefined
+}
+
 /**
  * Resolve an import path to a file path.
  * @param importPath - The import path to resolve.
@@ -150,7 +170,7 @@ export function tryResolveImport(importPath: string) {
   const specifiedVersion = match[2] // "1.2.3" (optional)
   const relativePath = match[3] // "/path/to/file.sol"
 
-  const packageRoot = resolvePkg(basePackage)
+  const packageRoot = resolvePkgRoot(basePackage)
   if (!packageRoot) {
     throw new Error(`Package ${basePackage} not found.`)
   }