github.com/julienschmidt/httprouter v1.3.0: Param

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 github.com/julienschmidt/httprouter.Param in pkg:golang/github.com/julienschmidt/httprouter@v1.3.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/julienschmidt/httprouter@v1.3.0
Demonstrate these symbols/APIs:
  - github.com/julienschmidt/httprouter.Param

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:fd39d964f7ad25616f39703c022cf43a66857c55805285985dde9a431f27de59","contract":["httprouter.Param stores URL parameter key and value pairs as exported string fields","httprouter.Params is an ordered slice of httprouter.Param elements accessible by index","httprouter.Params ByName retrieves the value corresponding to an existing parameter key","httprouter.Params ByName returns an empty string when the queried key does not exist","Router extracts named route wildcards into httprouter.Param instances passed to the Handle callback","Router extracts multiple named route wildcards and wildcard catch-all parameters into ordered httprouter.Param elements"],"goal":"verify github.com/julienschmidt/httprouter.Param in pkg:golang/github.com/julienschmidt/httprouter@v1.3.0","kind":"HOW","packages":["pkg:golang/github.com/julienschmidt/httprouter@v1.3.0"],"schemaVersion":1,"symbols":["github.com/julienschmidt/httprouter.Param"]},"contractCommand":["go","run","./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/julienschmidt/httprouter@v1.3.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/julienschmidt/httprouter@v1.3.0","symbols":["github.com/julienschmidt/httprouter.Param"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/julienschmidt/httprouter v1.3.0

github.com/julienschmidt/httprouter v1.3.0 h1:U0609e9tgbseu3rBINet9P48AI/D3oJs4dN7jwJOQ1U=
github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=

package main

import (
	"fmt"
	"net/http"
	"net/http/httptest"

	"github.com/julienschmidt/httprouter"
)

func main() {
	router := httprouter.New()

	router.GET("/users/:id", func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
		idParam := ps.ByName("id")
		fmt.Fprintf(w, "User ID: %s\n", idParam)
		for _, p := range ps {
			fmt.Printf("Param key=%s value=%s\n", p.Key, p.Value)
		}
	})

	req := httptest.NewRequest(http.MethodGet, "/users/42", nil)
	rec := httptest.NewRecorder()
	router.ServeHTTP(rec, req)

	fmt.Printf("Status: %d, Body: %s", rec.Code, rec.Body.String())
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/julienschmidt/httprouter.Param in pkg:golang/github.com/julienschmidt/httprouter@v1.3.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/julienschmidt/httprouter@v1.3.0"
  ],
  "symbols": [
    "github.com/julienschmidt/httprouter.Param"
  ]
}

package main

import (
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"

	"github.com/julienschmidt/httprouter"
)

func main() {
	// Assertion 1: httprouter.Param stores URL parameter key and value pairs as exported string fields
	{
		p := httprouter.Param{
			Key:   "category",
			Value: "books",
		}
		if p.Key != "category" || p.Value != "books" {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: expected Key='category', Value='books', got Key=%q, Value=%q\n", p.Key, p.Value)
			os.Exit(1)
		}
	}

	// Assertion 2: httprouter.Params is an ordered slice of httprouter.Param elements accessible by index
	{
		ps := httprouter.Params{
			{Key: "section", Value: "tech"},
			{Key: "article", Value: "101"},
		}
		if len(ps) != 2 {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected len 2, got %d\n", len(ps))
			os.Exit(1)
		}
		if ps[0].Key != "section" || ps[0].Value != "tech" {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: index 0 mismatch: %+v\n", ps[0])
			os.Exit(1)
		}
		if ps[1].Key != "article" || ps[1].Value != "101" {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: index 1 mismatch: %+v\n", ps[1])
			os.Exit(1)
		}
	}

	// Assertion 3: httprouter.Params ByName retrieves the value corresponding to an existing parameter key
	{
		ps := httprouter.Params{
			{Key: "lang", Value: "golang"},
			{Key: "version", Value: "1.3.0"},
		}
		val := ps.ByName("lang")
		if val != "golang" {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: expected 'golang', got %q\n", val)
			os.Exit(1)
		}
		val2 := ps.ByName("version")
		if val2 != "1.3.0" {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: expected '1.3.0', got %q\n", val2)
			os.Exit(1)
		}
	}

	// Assertion 4: httprouter.Params ByName returns an empty string when the queried key does not exist
	{
		ps := httprouter.Params{
			{Key: "name", Value: "test"},
		}
		val := ps.ByName("missing")
		if val != "" {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: expected empty string, got %q\n", val)
			os.Exit(1)
		}
	}

	// Assertion 5: Router extracts named route wildcards into httprouter.Param instances passed to the Handle callback
	{
		router := httprouter.New()
		var capturedParams httprouter.Params
		var called bool

		router.GET("/items/:itemId", func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
			called = true
			capturedParams = ps
			w.WriteHeader(http.StatusOK)
		})

		req := httptest.NewRequest(http.MethodGet, "/items/sku-9876", nil)
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, req)

		if !called {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: route handler was not called\n")
			os.Exit(1)
		}
		if rec.Code != http.StatusOK {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: expected status 200, got %d\n", rec.Code)
			os.Exit(1)
		}
		if len(capturedParams) != 1 {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: expected 1 param, got %d\n", len(capturedParams))
			os.Exit(1)
		}
		p := capturedParams[0]
		if p.Key != "itemId" || p.Value != "sku-9876" {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: param mismatch: Key=%q, Value=%q\n", p.Key, p.Value)
			os.Exit(1)
		}
		if capturedParams.ByName("itemId") != "sku-9876" {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: ByName mismatch: got %q\n", capturedParams.ByName("itemId"))
			os.Exit(1)
		}
	}

	// Assertion 6: Router extracts multiple named route wildcards and wildcard catch-all parameters into ordered httprouter.Param elements
	{
		router := httprouter.New()
		var capturedParams httprouter.Params
		var called bool

		router.GET("/orgs/:orgId/repos/:repoName/*subpath", func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
			called = true
			capturedParams = ps
			w.WriteHeader(http.StatusOK)
		})

		req := httptest.NewRequest(http.MethodGet, "/orgs/golang/repos/go/src/net/http", nil)
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, req)

		if !called {
			fmt.Fprintf(os.Stderr, "assertion 6 failed: route handler was not called\n")
			os.Exit(1)
		}
		if len(capturedParams) != 3 {
			fmt.Fprintf(os.Stderr, "assertion 6 failed: expected 3 params, got %d\n", len(capturedParams))
			os.Exit(1)
		}
		if capturedParams[0].Key != "orgId" || capturedParams[0].Value != "golang" {
			fmt.Fprintf(os.Stderr, "assertion 6 failed: param 0 mismatch: %+v\n", capturedParams[0])
			os.Exit(1)
		}
		if capturedParams[1].Key != "repoName" || capturedParams[1].Value != "go" {
			fmt.Fprintf(os.Stderr, "assertion 6 failed: param 1 mismatch: %+v\n", capturedParams[1])
			os.Exit(1)
		}
		if capturedParams[2].Key != "subpath" || capturedParams[2].Value != "/src/net/http" {
			fmt.Fprintf(os.Stderr, "assertion 6 failed: param 2 mismatch: %+v\n", capturedParams[2])
			os.Exit(1)
		}
	}

	fmt.Println("All contract assertions passed successfully.")
}