feat: Generate DB unique constraints as enums (#3701)

* feat: Generate DB unique constraints as enums

This fixes a TODO from #3409.

coderd/database/gen/dump/main.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+	"bytes"
+	"database/sql"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+
+	"github.com/coder/coder/coderd/database"
+	"github.com/coder/coder/coderd/database/postgres"
+)
+
+func main() {
+	connection, closeFn, err := postgres.Open()
+	if err != nil {
+		panic(err)
+	}
+	defer closeFn()
+
+	db, err := sql.Open("postgres", connection)
+	if err != nil {
+		panic(err)
+	}
+
+	err = database.MigrateUp(db)
+	if err != nil {
+		panic(err)
+	}
+
+	cmd := exec.Command(
+		"docker",
+		"run",
+		"--rm",
+		"--network=host",
+		"postgres:13",
+		"pg_dump",
+		"--schema-only",
+		connection,
+		"--no-privileges",
+		"--no-owner",
+
+		// We never want to manually generate
+		// queries executing against this table.
+		"--exclude-table=schema_migrations",
+	)
+
+	cmd.Env = append(os.Environ(), []string{
+		"PGTZ=UTC",
+		"PGCLIENTENCODING=UTF8",
+	}...)
+	var output bytes.Buffer
+	cmd.Stdout = &output
+	cmd.Stderr = os.Stderr
+	err = cmd.Run()
+	if err != nil {
+		panic(err)
+	}
+
+	for _, sed := range []string{
+		// Remove all comments.
+		"/^--/d",
+		// Public is implicit in the schema.
+		"s/ public\\./ /",
+		// Remove database settings.
+		"s/SET .* = .*;//g",
+		// Remove select statements. These aren't useful
+		// to a reader of the dump.
+		"s/SELECT.*;//g",
+		// Removes multiple newlines.
+		"/^$/N;/^\\n$/D",
+	} {
+		cmd := exec.Command("sed", "-e", sed)
+		cmd.Stdin = bytes.NewReader(output.Bytes())
+		output = bytes.Buffer{}
+		cmd.Stdout = &output
+		cmd.Stderr = os.Stderr
+		err = cmd.Run()
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	dump := fmt.Sprintf("-- Code generated by 'make coderd/database/generate'. DO NOT EDIT.\n%s", output.Bytes())
+	_, mainPath, _, ok := runtime.Caller(0)
+	if !ok {
+		panic("couldn't get caller path")
+	}
+	err = os.WriteFile(filepath.Join(mainPath, "..", "..", "..", "dump.sql"), []byte(dump), 0o600)
+	if err != nil {
+		panic(err)
+	}
+}

coderd/database/gen/enum/main.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"golang.org/x/xerrors"
+)
+
+const header = `// Code generated by gen/enum. DO NOT EDIT.
+package database
+`
+
+func main() {
+	if err := run(); err != nil {
+		panic(err)
+	}
+}
+
+func run() error {
+	dump, err := os.Open("dump.sql")
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "error: %s must be run in the database directory with dump.sql present\n", os.Args[0])
+		return err
+	}
+	defer dump.Close()
+
+	var uniqueConstraints []string
+
+	s := bufio.NewScanner(dump)
+	query := ""
+	for s.Scan() {
+		line := strings.TrimSpace(s.Text())
+		switch {
+		case strings.HasPrefix(line, "--"):
+		case line == "":
+		case strings.HasSuffix(line, ";"):
+			query += line
+			if isUniqueConstraint(query) {
+				uniqueConstraints = append(uniqueConstraints, query)
+			}
+			query = ""
+		default:
+			query += line + " "
+		}
+	}
+	if err = s.Err(); err != nil {
+		return err
+	}
+
+	return writeContents("unique_constraint.go", uniqueConstraints, generateUniqueConstraints)
+}
+
+func isUniqueConstraint(query string) bool {
+	return strings.Contains(query, "UNIQUE")
+}
+
+func generateUniqueConstraints(queries []string) ([]byte, error) {
+	s := &bytes.Buffer{}
+
+	_, _ = fmt.Fprint(s, header)
+	_, _ = fmt.Fprint(s, `
+// UniqueConstraint represents a named unique constraint on a table.
+type UniqueConstraint string
+
+// UniqueConstraint enums.
+const (
+`)
+	for _, query := range queries {
+		name := ""
+		switch {
+		case strings.Contains(query, "ALTER TABLE") && strings.Contains(query, "ADD CONSTRAINT"):
+			name = strings.Split(query, " ")[6]
+		case strings.Contains(query, "CREATE UNIQUE INDEX"):
+			name = strings.Split(query, " ")[3]
+		default:
+			return nil, xerrors.Errorf("unknown unique constraint format: %s", query)
+		}
+		_, _ = fmt.Fprintf(s, "\tUnique%s UniqueConstraint = %q // %s\n", nameFromSnakeCase(name), name, query)
+	}
+	_, _ = fmt.Fprint(s, ")\n")
+
+	return s.Bytes(), nil
+}
+
+func writeContents[T any](dest string, arg T, fn func(T) ([]byte, error)) error {
+	b, err := fn(arg)
+	if err != nil {
+		return err
+	}
+	err = os.WriteFile(dest, b, 0o600)
+	if err != nil {
+		return err
+	}
+	cmd := exec.Command("goimports", "-w", dest)
+	return cmd.Run()
+}
+
+func nameFromSnakeCase(s string) string {
+	var ret string
+	for _, ss := range strings.Split(s, "_") {
+		switch ss {
+		case "id":
+			ret += "ID"
+		case "ids":
+			ret += "IDs"
+		case "jwt":
+			ret += "JWT"
+		case "idx":
+			ret += "Index"
+		default:
+			ret += strings.Title(ss)
+		}
+	}
+	return ret
+}