From 3572646d5e0804f85bc7f64633fb95722533f9dd Mon Sep 17 00:00:00 2001
From: Tim <hello@timsmart.co>
Date: Thu, 13 Jun 2024 01:21:09 +1200
Subject: [PATCH] ensure multiline error messages are preserved in cause
 rendering (#2981)

---
 .changeset/long-tools-sleep.md                      |  5 +++++
 packages/effect/src/internal/cause.ts               |  2 +-
 packages/effect/test/Effect/cause-rendering.test.ts | 13 +++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/long-tools-sleep.md

diff --git a/.changeset/long-tools-sleep.md b/.changeset/long-tools-sleep.md
new file mode 100644
index 0000000000..5603b9ff1f
--- /dev/null
+++ b/.changeset/long-tools-sleep.md
@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+ensure multiline error messages are preserved in cause rendering
diff --git a/packages/effect/src/internal/cause.ts b/packages/effect/src/internal/cause.ts
index dda5d700ad..27b328667f 100644
--- a/packages/effect/src/internal/cause.ts
+++ b/packages/effect/src/internal/cause.ts
@@ -1055,7 +1055,7 @@ export const spanToTrace = globalValue("effect/Tracer/spanToTrace", () => new We
 
 const prettyErrorStack = (message: string, stack: string, span?: Span | undefined): string => {
   const out: Array<string> = [message]
-  const lines = stack.split("\n")
+  const lines = stack.startsWith(message) ? stack.slice(message.length).split("\n") : stack.split("\n")
 
   for (let i = 1; i < lines.length; i++) {
     if (lines[i].includes("Generator.next")) {
diff --git a/packages/effect/test/Effect/cause-rendering.test.ts b/packages/effect/test/Effect/cause-rendering.test.ts
index 8d8ea1191b..058fa163c3 100644
--- a/packages/effect/test/Effect/cause-rendering.test.ts
+++ b/packages/effect/test/Effect/cause-rendering.test.ts
@@ -141,4 +141,17 @@ describe("Effect", () => {
       yield* Effect.void
       it.expect({ foo: "ok" }).toStrictEqual({ foo: "bar" })
     }))
+
+  it.effect("multiline message", () =>
+    Effect.gen(function*() {
+      const cause = yield* Effect.fail(new Error("Multi-line\nerror\nmessage")).pipe(
+        Effect.sandbox,
+        Effect.flip
+      )
+      const pretty = Cause.pretty(cause)
+      assert.isTrue(pretty.startsWith(`Error: Multi-line
+error
+message
+    at`))
+    }))
 })