From 0d32de703737735cad97631fff4126bb3bd9f115 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 17 Dec 2024 17:58:02 +0100
Subject: [PATCH] Carry both call-site and definition site in Effect.fn,
 auto-trace to anon

---
 .changeset/weak-pears-remember.md     |  5 +++++
 packages/effect/src/Effect.ts         | 29 ++++++++++++++++++++++++---
 packages/effect/src/internal/cause.ts | 10 +++++----
 3 files changed, 37 insertions(+), 7 deletions(-)
 create mode 100644 .changeset/weak-pears-remember.md

diff --git a/.changeset/weak-pears-remember.md b/.changeset/weak-pears-remember.md
new file mode 100644
index 00000000000..e28a4dd11f2
--- /dev/null
+++ b/.changeset/weak-pears-remember.md
@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Carry both call-site and definition site in Effect.fn, auto-trace to anon
diff --git a/packages/effect/src/Effect.ts b/packages/effect/src/Effect.ts
index d4a2aeb5a28..1d7b3bd0079 100644
--- a/packages/effect/src/Effect.ts
+++ b/packages/effect/src/Effect.ts
@@ -10130,9 +10130,31 @@ export const fn:
     name: string,
     options?: Tracer.SpanOptions
   ) => fn.Gen & fn.NonGen) = function(nameOrBody: Function | string, ...pipeables: Array<any>) {
+    const limit = Error.stackTraceLimit
+    Error.stackTraceLimit = 2
+    const error0 = new Error()
+    Error.stackTraceLimit = limit
     if (typeof nameOrBody !== "string") {
-      return function(this: any) {
-        return fnApply(this, nameOrBody, arguments as any, pipeables)
+      return function(this: any, ...args: Array<any>) {
+        const limit = Error.stackTraceLimit
+        Error.stackTraceLimit = 2
+        const error = new Error()
+        Error.stackTraceLimit = limit
+        let cache: false | string = false
+        const captureStackTrace = () => {
+          if (cache !== false) {
+            return cache
+          }
+          if (error.stack) {
+            const stack0 = error0.stack!.trim().split("\n")
+            const stack = error.stack.trim().split("\n")
+            cache = `${stack0.slice(2).join("\n").trim()}\n${stack.slice(2).join("\n").trim()}`
+            return cache
+          }
+        }
+        const effect = fnApply(this, nameOrBody, args, pipeables)
+        const opts: any = { captureStackTrace }
+        return withSpan(effect, "<anonymous>", opts)
       } as any
     }
     const name = nameOrBody
@@ -10149,8 +10171,9 @@ export const fn:
             return cache
           }
           if (error.stack) {
+            const stack0 = error0.stack!.trim().split("\n")
             const stack = error.stack.trim().split("\n")
-            cache = stack.slice(2).join("\n").trim()
+            cache = `${stack0.slice(2).join("\n").trim()}\n${stack.slice(2).join("\n").trim()}`
             return cache
           }
         }
diff --git a/packages/effect/src/internal/cause.ts b/packages/effect/src/internal/cause.ts
index 38bcbb4ddd1..8ca4623142a 100644
--- a/packages/effect/src/internal/cause.ts
+++ b/packages/effect/src/internal/cause.ts
@@ -1073,7 +1073,7 @@ export const prettyErrorMessage = (u: unknown): string => {
   return stringifyCircular(u)
 }
 
-const locationRegex = /\((.*)\)/
+const locationRegex = /\((.*)\)/g
 
 /** @internal */
 export const spanToTrace = globalValue("effect/Tracer/spanToTrace", () => new WeakMap())
@@ -1105,9 +1105,11 @@ const prettyErrorStack = (message: string, stack: string, span?: Span | undefine
       if (typeof stackFn === "function") {
         const stack = stackFn()
         if (typeof stack === "string") {
-          const locationMatch = stack.match(locationRegex)
-          const location = locationMatch ? locationMatch[1] : stack.replace(/^at /, "")
-          out.push(`    at ${current.name} (${location})`)
+          const locationMatchAll = stack.matchAll(locationRegex)
+          for (const locationMatch of locationMatchAll) {
+            const location = locationMatch ? locationMatch[1] : stack.replace(/^at /, "")
+            out.push(`    at ${current.name} (${location})`)
+          }
         } else {
           out.push(`    at ${current.name}`)
         }