github.com/go-stack/stack v1.8.0: CallStack.TrimBelow

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:golang/github.com/go-stack/stack@v1.8.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/go-stack/stack@v1.8.0
Demonstrate these symbols/APIs:
  - stack.CallStack.TrimBelow

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

package sample

import (
	"testing"

	"github.com/go-stack/stack"
)

func levelThree() (stack.Call, stack.CallStack) {
	// target is the caller of levelThree, i.e., levelTwo
	trace := stack.Trace()
	if len(trace) < 2 {
		panic("trace too short")
	}
	target := trace[1]
	return target, trace
}

func levelTwo() (stack.Call, stack.CallStack) {
	return levelThree()
}

func levelOne() (stack.Call, stack.CallStack) {
	return levelTwo()
}

func unrelatedCall() stack.Call {
	return stack.Caller(0)
}

func TestTrimBelowRemovesFramesBeforeSpecifiedCall(t *testing.T) {
	target, trace := levelOne()
	if len(trace) < 3 {
		t.Fatalf("expected trace to have at least 3 frames, got %d", len(trace))
	}

	trimmed := trace.TrimBelow(target)
	if len(trimmed) == 0 {
		t.Fatalf("expected trimmed trace to be non-empty")
	}

	// target should be the innermost (first) frame in trimmed
	if trimmed[0].Frame().Function != target.Frame().Function {
		t.Fatalf("expected first frame to be %q, got %q", target.Frame().Function, trimmed[0].Frame().Function)
	}

	// Ensure frames before target were actually removed
	if len(trimmed) >= len(trace) {
		t.Fatalf("expected trimmed length (%d) to be strictly less than trace length (%d)", len(trimmed), len(trace))
	}
}

func TestTrimBelowPreservesCallerFramesAboveSpecifiedCall(t *testing.T) {
	target, trace := levelOne()
	trimmed := TrimBelowCall(trace, target)

	// Target was trace[1], so trimmed should match trace[1:]
	if len(trimmed) != len(trace)-1 {
		t.Fatalf("expected trimmed length %d, got %d", len(trace)-1, len(trimmed))
	}

	for i := range trimmed {
		orig := trace[1+i].Frame()
		curr := trimmed[i].Frame()
		if curr.Function != orig.Function || curr.File != orig.File || curr.Line != orig.Line {
			t.Fatalf("mismatch at frame %d: expected %s:%d, got %s:%d", i, orig.Function, orig.Line, curr.Function, curr.Line)
		}
	}
}

func TestTrimBelowEmptyWhenCallNotFound(t *testing.T) {
	unrelated := unrelatedCall()
	trace := stack.Trace()

	trimmed := trace.TrimBelow(unrelated)
	if len(trimmed) != 0 {
		t.Fatalf("expected empty CallStack when target is not present, got length %d", len(trimmed))
	}
}

{"case":{"caseId":"case:sha256:9ab16b0b0a20c736a0d3d5caf5d3456ff9e9ce41dc8c35435ead00015328896d","contract":["stack.CallStack.TrimBelow removes frames before the specified Call making it the innermost frame","stack.CallStack.TrimBelow preserves all caller frames above the specified Call","stack.CallStack.TrimBelow produces an empty stack when the specified Call is not present in the trace"],"goal":"verify pkg:golang/github.com/go-stack/stack@v1.8.0","kind":"HOW","packages":["pkg:golang/github.com/go-stack/stack@v1.8.0"],"schemaVersion":1,"symbols":["stack.CallStack.TrimBelow"]},"contractCommand":["go","test","./..."],"environment":{"arch":"amd64","compiler":"go","compilerVersion":"1.26.6","distro":"ubuntu","ecosystem":"golang","language":"go","languageVersion":"1.26.6","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/go-stack/stack@v1.8.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/go-stack/stack@v1.8.0","symbols":["stack.CallStack.TrimBelow"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/go-stack/stack v1.8.0

github.com/go-stack/stack v1.8.0 h1:5SgMzNM5HxrEjV0ww2lTmX6E2Izsfxas4+YHWRs3Lsk=
github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=

package sample

import (
	"github.com/go-stack/stack"
)

// TrimBelowCaller captures the current trace and trims all frames below the specified Call.
// If the target Call is present in the stack, it becomes the first (innermost) frame of the returned CallStack.
func TrimBelowCaller(target stack.Call) stack.CallStack {
	trace := stack.Trace()
	return trace.TrimBelow(target)
}

// TrimBelowCall trims frames from an existing CallStack below the specified target Call.
func TrimBelowCall(cs stack.CallStack, target stack.Call) stack.CallStack {
	return cs.TrimBelow(target)
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/go-stack/stack@v1.8.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/go-stack/stack@v1.8.0"
  ],
  "symbols": [
    "stack.CallStack.TrimBelow"
  ]
}