From 759a8af1d79c9205ce5719c329736214f62c6331 Mon Sep 17 00:00:00 2001
From: morgansliman <morgansliman@gmail.com>
Date: Mon, 25 Oct 2021 10:56:35 -0400
Subject: [PATCH] Enable user configurable tsconfig path

---
 packages/hardhat-core/src/internal/cli/cli.ts |  2 +-
 .../internal/core/params/hardhat-params.ts    |  4 +-
 .../src/internal/core/typescript-support.ts   |  6 ++-
 packages/hardhat-core/src/register.ts         |  2 +-
 .../typescript-project/test/tsconfig.json     |  1 +
 .../test/internal/core/typescript-support.ts  | 39 +++++++++++++++++++
 6 files changed, 49 insertions(+), 5 deletions(-)
 create mode 100644 packages/hardhat-core/test/fixture-projects/typescript-project/test/tsconfig.json

diff --git a/packages/hardhat-core/src/internal/cli/cli.ts b/packages/hardhat-core/src/internal/cli/cli.ts
index f09328a1be..83a5d19a7f 100755
--- a/packages/hardhat-core/src/internal/cli/cli.ts
+++ b/packages/hardhat-core/src/internal/cli/cli.ts
@@ -121,7 +121,7 @@ async function main() {
     }
 
     if (willRunWithTypescript(hardhatArguments.config)) {
-      loadTsNode();
+      loadTsNode(hardhatArguments.tsconfig);
     }
 
     let taskName = parsedTaskName ?? TASK_HELP;
diff --git a/packages/hardhat-core/src/internal/core/params/hardhat-params.ts b/packages/hardhat-core/src/internal/core/params/hardhat-params.ts
index e541899abf..19234878cd 100644
--- a/packages/hardhat-core/src/internal/core/params/hardhat-params.ts
+++ b/packages/hardhat-core/src/internal/core/params/hardhat-params.ts
@@ -78,8 +78,8 @@ export const HARDHAT_PARAM_DEFINITIONS: HardhatParamDefinitions = {
   tsconfig: {
     name: "tsconfig",
     defaultValue: undefined,
-    description: "Reserved hardhat argument -- Has no effect.",
-    type: types.string,
+    description: "A TypeScript config file.",
+    type: types.inputFile,
     isOptional: true,
     isFlag: false,
     isVariadic: false,
diff --git a/packages/hardhat-core/src/internal/core/typescript-support.ts b/packages/hardhat-core/src/internal/core/typescript-support.ts
index 6c27a858e8..f9c1c7e44c 100644
--- a/packages/hardhat-core/src/internal/core/typescript-support.ts
+++ b/packages/hardhat-core/src/internal/core/typescript-support.ts
@@ -38,7 +38,7 @@ export function isTypescriptSupported() {
   return cachedIsTypescriptSupported;
 }
 
-export function loadTsNode() {
+export function loadTsNode(tsConfigPath?: string) {
   try {
     require.resolve("typescript");
   } catch (error) {
@@ -58,6 +58,10 @@ export function loadTsNode() {
     return;
   }
 
+  if (tsConfigPath !== undefined) {
+    process.env.TS_NODE_PROJECT = tsConfigPath;
+  }
+
   // See: https://github.com/nomiclabs/hardhat/issues/265
   if (process.env.TS_NODE_FILES === undefined) {
     process.env.TS_NODE_FILES = "true";
diff --git a/packages/hardhat-core/src/register.ts b/packages/hardhat-core/src/register.ts
index f3858837de..f1c13713f5 100644
--- a/packages/hardhat-core/src/register.ts
+++ b/packages/hardhat-core/src/register.ts
@@ -36,7 +36,7 @@ if (!HardhatContext.isCreated()) {
   }
 
   if (willRunWithTypescript(hardhatArguments.config)) {
-    loadTsNode();
+    loadTsNode(hardhatArguments.tsconfig);
   }
 
   const config = loadConfigAndTasks(hardhatArguments);
diff --git a/packages/hardhat-core/test/fixture-projects/typescript-project/test/tsconfig.json b/packages/hardhat-core/test/fixture-projects/typescript-project/test/tsconfig.json
new file mode 100644
index 0000000000..0967ef424b
--- /dev/null
+++ b/packages/hardhat-core/test/fixture-projects/typescript-project/test/tsconfig.json
@@ -0,0 +1 @@
+{}
diff --git a/packages/hardhat-core/test/internal/core/typescript-support.ts b/packages/hardhat-core/test/internal/core/typescript-support.ts
index 39b29807fe..13454eb28a 100644
--- a/packages/hardhat-core/test/internal/core/typescript-support.ts
+++ b/packages/hardhat-core/test/internal/core/typescript-support.ts
@@ -5,6 +5,7 @@ import { TASK_TEST_GET_TEST_FILES } from "../../../src/builtin-tasks/task-names"
 import { resetHardhatContext } from "../../../src/internal/reset";
 import { useEnvironment } from "../../helpers/environment";
 import { useFixtureProject } from "../../helpers/project";
+import { HardhatError } from "../../../src/internal/core/errors";
 
 describe("Typescript support", function () {
   describe("strict typescript config", function () {
@@ -58,3 +59,41 @@ describe("Typescript support", function () {
     });
   });
 });
+
+describe("tsconfig param", function () {
+  useFixtureProject("typescript-project");
+  describe("When setting an incorrect tsconfig file", function () {
+    beforeEach(() => {
+      process.env.HARDHAT_TSCONFIG = "non-existent.ts";
+    });
+
+    afterEach(() => {
+      delete process.env.HARDHAT_TSCONFIG;
+      resetHardhatContext();
+    });
+
+    it("should fail to load hardhat", function () {
+      assert.throws(
+        () => require("../../../src/internal/lib/hardhat-lib"),
+        HardhatError
+      );
+    });
+  });
+
+  describe("When setting a correct tsconfig file", function () {
+    beforeEach(() => {
+      process.env.HARDHAT_TSCONFIG = "./test/tsconfig.json";
+    });
+
+    afterEach(() => {
+      delete process.env.HARDHAT_TSCONFIG;
+      resetHardhatContext();
+    });
+
+    it("should load hardhat", function () {
+      assert.doesNotThrow(() =>
+        require("../../../src/internal/lib/hardhat-lib")
+      );
+    });
+  });
+});