Add support for custom tsconfig.json (#2089)

Use `--config`

4 files changed, 25 insertions, 0 deletions

diff --git a/tests/config.test b/tests/config.test
new file mode 100644
index 000000000..ee811ab8b
--- /dev/null
+++ b/tests/config.test
@@ -0,0 +1,4 @@
+args: --reload --config tests/config.tsconfig.json tests/config.ts
+check_stderr: true
+exit_code: 1
+output: tests/config.ts.out
diff --git a/tests/config.ts b/tests/config.ts
new file mode 100644
index 000000000..e08061e77
--- /dev/null
+++ b/tests/config.ts
@@ -0,0 +1,5 @@
+const map = new Map<string, { foo: string }>();
+
+if (map.get("bar").foo) {
+  console.log("here");
+}
diff --git a/tests/config.ts.out b/tests/config.ts.out
new file mode 100644
index 000000000..e3ceb52bc
--- /dev/null
+++ b/tests/config.ts.out
@@ -0,0 +1,9 @@
+Unsupported compiler options in "[WILDCARD]tests/config.tsconfig.json"
+  The following options were ignored:
+    module, target
+Compiling file://[WILDCARD]tests/config.ts
+[WILDCARD]tests/config.ts:3:5 - error TS2532: Object is possibly 'undefined'.
+
+3 if (map.get("bar").foo) {
+      ~~~~~~~~~~~~~~
+
diff --git a/tests/config.tsconfig.json b/tests/config.tsconfig.json
new file mode 100644
index 000000000..074d7ac0b
--- /dev/null
+++ b/tests/config.tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "module": "amd",
+    "strict": true,
+    "target": "es5"
+  }
+}