google.golang.org/appengine v1.2.0: Namespace

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 google.golang.org/appengine.Namespace in pkg:golang/google.golang.org/appengine@v1.2.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/google.golang.org/appengine@v1.2.0
Demonstrate these symbols/APIs:
  - google.golang.org/appengine.Namespace

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.

{"case":{"caseId":"case:sha256:5c9acb808b5d97f5ad76632a244af52a4cee5b5d037c2b870b38b1a3d0ed556f","contract":["appengine.Namespace(ctx, namespace) accepts empty string and strings of 1..100 characters matching ^[0-9A-Za-z._-]{0,100}$ and returns a non-nil namespaced context with nil error","appengine.Namespace(ctx, namespace) rejects strings containing characters outside [0-9A-Za-z._-] or longer than 100 characters, returning nil context and an error matching 'appengine: namespace ... does not match'"],"goal":"verify google.golang.org/appengine.Namespace in pkg:golang/google.golang.org/appengine@v1.2.0","kind":"HOW","packages":["pkg:golang/google.golang.org/appengine@v1.2.0"],"schemaVersion":1,"symbols":["google.golang.org/appengine.Namespace"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/google.golang.org/appengine@v1.2.0"],"schemaVersion":1,"subject":"pkg:golang/google.golang.org/appengine@v1.2.0","symbols":["google.golang.org/appengine.Namespace"],"verifierAdapter":"golang@1"}

module sample

go 1.26.0

require google.golang.org/appengine v1.2.0

require (
	github.com/golang/protobuf v1.2.0 // indirect
	golang.org/x/net v0.0.0-20180724234803-3673e40ba225 // indirect
	golang.org/x/sync v0.24.0 // indirect
)

github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
golang.org/x/net v0.0.0-20180724234803-3673e40ba225 h1:kNX+jCowfMYzvlSvJu5pQWEmyWFrBXJ3PBy10xKMXK8=
golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
golang.org/x/sync v0.24.0 h1:iqiDrGoDgyuvAKrhLQthUEzU/R378N78gXbBjxed7oA=
golang.org/x/sync v0.24.0/go.mod h1:sUUOizhqBxiL6pEWpqNLUiaJn1ShEbZ6BBqskPbjZm0=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
google.golang.org/appengine v1.2.0 h1:S0iUepdCWODXRvtE+gcRDd15L+k+k1AiHlMiMjefH24=
google.golang.org/appengine v1.2.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=

{
  "schemaVersion": 1,
  "goal": "verify google.golang.org/appengine.Namespace in pkg:golang/google.golang.org/appengine@v1.2.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/google.golang.org/appengine@v1.2.0"
  ],
  "symbols": [
    "google.golang.org/appengine.Namespace"
  ]
}

package main

import (
	"context"
	"os"
	"strings"

	"google.golang.org/appengine"
)

func main() {
	baseCtx := context.Background()

	// Valid namespaces (empty, alphanumeric, '.', '_', '-', up to 100 chars)
	validNames := []string{
		"",
		"tenant-alpha_01.prod",
		 strings.Repeat("a", 100),
	}
	for _, ns := range validNames {
		ctx, err := appengine.Namespace(baseCtx, ns)
		if err != nil {
			os.Exit(1)
		}
		if ctx == nil {
			os.Exit(2)
		}
	}

	// Invalid namespaces (disallowed characters or length > 100)
	invalidNames := []string{
		"invalid space",
		"invalid/slash",
		"invalid?query",
		strings.Repeat("a", 101),
	}
	for _, ns := range invalidNames {
		ctx, err := appengine.Namespace(baseCtx, ns)
		if err == nil || ctx != nil {
			os.Exit(3)
		}
		if !strings.Contains(err.Error(), "does not match") {
			os.Exit(4)
		}
	}
}