fix library verification

bytecode of a library contains address of a deployed library

apps/explorer/lib/explorer/smart_contract/verifier.ex

@@ -69,7 +69,8 @@ defmodule Explorer.SmartContract.Verifier do
     blockchain_bytecode_without_whisper = extract_bytecode(blockchain_bytecode)
 
     cond do
-      generated_bytecode != blockchain_bytecode_without_whisper ->
+      generated_bytecode != blockchain_bytecode_without_whisper &&
+          !try_library_verification(generated_bytecode, blockchain_bytecode_without_whisper) ->
         {:error, :generated_bytecode}
 
       has_constructor_with_params?(abi) &&
@@ -81,6 +82,17 @@ defmodule Explorer.SmartContract.Verifier do
     end
   end
 
+  defp try_library_verification(
+         "730000000000000000000000000000000000000000" <> bytecode,
+         <<_address::binary-size(42)>> <> bytecode
+       ) do
+    true
+  end
+
+  defp try_library_verification(_, _) do
+    false
+  end
+
   @doc """
   In order to discover the bytecode we need to remove the `swarm source` from
   the hash.

apps/explorer/test/explorer/smart_contract/verifier_test.exs

@@ -144,6 +144,34 @@ defmodule Explorer.SmartContract.VerifierTest do
       assert abi != nil
     end
 
+    test "verifies a library" do
+      bytecode =
+        "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"
+
+      contract_address = insert(:contract_address, contract_code: bytecode)
+
+      code = """
+      pragma solidity 0.5.11;
+
+      library Foo {
+          function foo() external pure returns (string memory) {
+              return "foo";
+          }
+      }
+      """
+
+      params = %{
+        "contract_source_code" => code,
+        "compiler_version" => "v0.5.11+commit.c082d0b4",
+        "evm_version" => "default",
+        "name" => "Foo",
+        "optimization" => true
+      }
+
+      assert {:ok, %{abi: abi}} = Verifier.evaluate_authenticity(contract_address.hash, params)
+      assert abi != nil
+    end
+
     test "verifies smart contract compiled with Solidity 0.5.9 (includes new metadata in bytecode) with constructor args" do
       path = File.cwd!() <> "/test/support/fixture/smart_contract/solidity_0.5.9_smart_contract.sol"
       contract = File.read!(path)