github.com/jackc/pgx/v5 v5.11.0: StrictStructArgs

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/jackc/pgx/v5.StrictStructArgs in pkg:golang/github.com/jackc/pgx/v5@v5.11.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/jackc/pgx/v5@v5.11.0
Demonstrate these symbols/APIs:
  - github.com/jackc/pgx/v5.StrictStructArgs

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:sha256:1113b83a2671722b3ed1dc2f1b8f41c8abbd2fa62b353b4ddd10fef993a31017","contract":["pgx.StrictStructArgs rewrites @-named parameters in SQL into positional placeholders ($1, $2) using struct fields with db tags","pgx.StrictStructArgs falls back to struct field names when db tags are not specified","pgx.StrictStructArgs accepts a pointer to struct as well as a struct value","pgx.StrictStructArgs returns an error when SQL query references missing arguments not present in the struct","pgx.StrictStructArgs returns an error when extra arguments in the struct are not referenced in the SQL query","pgx.StrictStructArgs returns an error when argument is nil or not a struct","pgx.StrictStructArgs ignores unexported fields and fields tagged with db:\"-\""],"goal":"verify github.com/jackc/pgx/v5.StrictStructArgs in pkg:golang/github.com/jackc/pgx/v5@v5.11.0","kind":"HOW","packages":["pkg:golang/github.com/jackc/pgx/v5@v5.11.0"],"schemaVersion":1,"symbols":["github.com/jackc/pgx/v5.StrictStructArgs"]},"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/github.com/jackc/pgx/v5@v5.11.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/jackc/pgx/v5@v5.11.0","symbols":["github.com/jackc/pgx/v5.StrictStructArgs"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/jackc/pgx/v5 v5.11.0

require (
	github.com/jackc/pgpassfile v1.0.0 // indirect
	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
	golang.org/x/text v0.29.0 // indirect
)

github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
github.com/jackc/pgx/v5 v5.11.0 h1:IzBBtyK9AHqf98cctWFifYSci2hgQR/cd56wB4p+ogg=
github.com/jackc/pgx/v5 v5.11.0/go.mod h1:mal1tBGAFfLHvZzaYh77YS/eC6IX9OWbRV1QIIM0Jn4=
github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
golang.org/x/sync v0.17.0 h1:l60nONMj9l5drqw6jlhIELNv9I0A4OFgRsG9k2oT9Ug=
golang.org/x/sync v0.17.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
golang.org/x/text v0.29.0 h1:1neNs90w9YzJ9BocxfsQNHKuAT4pkghyXc4nhZ6sJvk=
golang.org/x/text v0.29.0/go.mod h1:7MhJOA9CD2qZyOKYazxdYMF85OwPdEr9jTtBpO7ydH4=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"context"
	"fmt"

	"github.com/jackc/pgx/v5"
)

type UserQuery struct {
	ID   int    `db:"id"`
	Role string `db:"role"`
}

func main() {
	queryArgs := UserQuery{
		ID:   42,
		Role: "admin",
	}

	rewriter := pgx.StrictStructArgs(queryArgs)
	sql, args, err := rewriter.RewriteQuery(
		context.Background(),
		nil,
		"SELECT username, email FROM users WHERE id = @id AND role = @role",
		nil,
	)
	if err != nil {
		fmt.Printf("RewriteQuery error: %v\n", err)
		return
	}

	fmt.Printf("Rewritten SQL: %s\n", sql)
	fmt.Printf("Arguments: %v\n", args)
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/jackc/pgx/v5.StrictStructArgs in pkg:golang/github.com/jackc/pgx/v5@v5.11.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/jackc/pgx/v5@v5.11.0"
  ],
  "symbols": [
    "github.com/jackc/pgx/v5.StrictStructArgs"
  ]
}

package main

import (
	"context"
	"fmt"
	"os"

	"github.com/jackc/pgx/v5"
)

func main() {
	if err := runContract(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract verification failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All github.com/jackc/pgx/v5.StrictStructArgs contract assertions passed successfully.")
}

func runContract() error {
	ctx := context.Background()

	// Assertion 1: pgx.StrictStructArgs rewrites @-named parameters in SQL into positional placeholders ($1, $2) using struct fields with db tags
	type QueryWithTags struct {
		ID   int    `db:"id"`
		Role string `db:"role"`
	}
	argsWithTags := QueryWithTags{ID: 101, Role: "admin"}
	rewriterWithTags := pgx.StrictStructArgs(argsWithTags)
	sqlWithTags, outArgsWithTags, err := rewriterWithTags.RewriteQuery(ctx, nil, "SELECT * FROM users WHERE id = @id AND role = @role", nil)
	if err != nil {
		return fmt.Errorf("assertion 1 failed: unexpected error: %w", err)
	}
	if sqlWithTags != "SELECT * FROM users WHERE id = $1 AND role = $2" {
		return fmt.Errorf("assertion 1 failed: expected positional SQL, got %q", sqlWithTags)
	}
	if len(outArgsWithTags) != 2 || outArgsWithTags[0] != 101 || outArgsWithTags[1] != "admin" {
		return fmt.Errorf("assertion 1 failed: unexpected args: %v", outArgsWithTags)
	}

	// Assertion 2: pgx.StrictStructArgs falls back to struct field names when db tags are not specified
	type QueryWithoutTags struct {
		UserID int
		Title  string
	}
	argsNoTag := QueryWithoutTags{UserID: 42, Title: "Engineer"}
	rewriterNoTag := pgx.StrictStructArgs(argsNoTag)
	sqlNoTag, outArgsNoTag, err := rewriterNoTag.RewriteQuery(ctx, nil, "SELECT * FROM staff WHERE UserID = @UserID AND Title = @Title", nil)
	if err != nil {
		return fmt.Errorf("assertion 2 failed: unexpected error: %w", err)
	}
	if sqlNoTag != "SELECT * FROM staff WHERE UserID = $1 AND Title = $2" {
		return fmt.Errorf("assertion 2 failed: expected SQL with field names, got %q", sqlNoTag)
	}
	if len(outArgsNoTag) != 2 || outArgsNoTag[0] != 42 || outArgsNoTag[1] != "Engineer" {
		return fmt.Errorf("assertion 2 failed: unexpected args: %v", outArgsNoTag)
	}

	// Assertion 3: pgx.StrictStructArgs accepts a pointer to struct as well as a struct value
	argsPtr := &QueryWithTags{ID: 202, Role: "manager"}
	rewriterPtr := pgx.StrictStructArgs(argsPtr)
	sqlPtr, outArgsPtr, err := rewriterPtr.RewriteQuery(ctx, nil, "SELECT * FROM users WHERE id = @id AND role = @role", nil)
	if err != nil {
		return fmt.Errorf("assertion 3 failed: unexpected error: %w", err)
	}
	if sqlPtr != "SELECT * FROM users WHERE id = $1 AND role = $2" {
		return fmt.Errorf("assertion 3 failed: expected rewritten SQL, got %q", sqlPtr)
	}
	if len(outArgsPtr) != 2 || outArgsPtr[0] != 202 || outArgsPtr[1] != "manager" {
		return fmt.Errorf("assertion 3 failed: unexpected args: %v", outArgsPtr)
	}

	// Assertion 4: pgx.StrictStructArgs returns an error when SQL query references missing arguments not present in the struct
	type SingleParam struct {
		ID int `db:"id"`
	}
	rewriterMissing := pgx.StrictStructArgs(SingleParam{ID: 1})
	_, _, err = rewriterMissing.RewriteQuery(ctx, nil, "SELECT * FROM users WHERE id = @id AND extra = @extra", nil)
	if err == nil {
		return fmt.Errorf("assertion 4 failed: expected error for missing argument, got nil")
	}

	// Assertion 5: pgx.StrictStructArgs returns an error when extra arguments in the struct are not referenced in the SQL query
	type ExtraParams struct {
		ID     int    `db:"id"`
		Unused string `db:"unused"`
	}
	rewriterExtra := pgx.StrictStructArgs(ExtraParams{ID: 1, Unused: "ignore"})
	_, _, err = rewriterExtra.RewriteQuery(ctx, nil, "SELECT * FROM users WHERE id = @id", nil)
	if err == nil {
		return fmt.Errorf("assertion 5 failed: expected error for unreferenced argument in strict mode, got nil")
	}

	// Assertion 6: pgx.StrictStructArgs returns an error when argument is nil or not a struct
	rewriterNil := pgx.StrictStructArgs(nil)
	_, _, err = rewriterNil.RewriteQuery(ctx, nil, "SELECT 1", nil)
	if err == nil {
		return fmt.Errorf("assertion 6 failed: expected error for nil input, got nil")
	}

	rewriterNonStruct := pgx.StrictStructArgs("not-a-struct")
	_, _, err = rewriterNonStruct.RewriteQuery(ctx, nil, "SELECT 1", nil)
	if err == nil {
		return fmt.Errorf("assertion 6 failed: expected error for non-struct input, got nil")
	}

	// Assertion 7: pgx.StrictStructArgs ignores unexported fields and fields tagged with db:"-"
	type StructWithIgnored struct {
		Active     bool   `db:"active"`
		ignoredTag string `db:"-"`
		unexported int
	}
	argsIgnored := StructWithIgnored{Active: true, ignoredTag: "skip", unexported: 99}
	rewriterIgnored := pgx.StrictStructArgs(argsIgnored)
	sqlIgnored, outArgsIgnored, err := rewriterIgnored.RewriteQuery(ctx, nil, "SELECT * FROM t WHERE active = @active", nil)
	if err != nil {
		return fmt.Errorf("assertion 7 failed: unexpected error: %w", err)
	}
	if sqlIgnored != "SELECT * FROM t WHERE active = $1" || len(outArgsIgnored) != 1 || outArgsIgnored[0] != true {
		return fmt.Errorf("assertion 7 failed: unexpected result: %q, %v", sqlIgnored, outArgsIgnored)
	}
	_, _, err = rewriterIgnored.RewriteQuery(ctx, nil, "SELECT * FROM t WHERE active = @active AND ignored = @ignoredTag", nil)
	if err == nil {
		return fmt.Errorf("assertion 7 failed: expected error referencing db:\"-\" field, got nil")
	}

	return nil
}