Embed the generator

Build a Go tool that checks your practice application's SQL and generates its code into a temporary directory.

Starting point

After the first six lessons, move to the supplied tool:

cd /tmp/seagull-practice/08_embedding

It reads the neighbouring 01_first_query application and needs no database connection. The supplied main.go has the imports and entry point ready.

Step 1: Construct the generator

Put this code inside run, before its final return nil:

	generator, err := seagull.New(dialect_engine_sqlite.New())
	if err != nil {
		return err
	}
	input := seagull.Input{Package: "store", Migrations: os.DirFS("../01_first_query"), MigrationDir: "db/migrations", QueryDir: "db/queries"}
	report, err := generator.Vet(ctx, input)
	if err != nil {
		return err
	}
	if err := report.Err(); err != nil {
		return err
	}
	result, err := generator.Generate(ctx, input)
	if err != nil {
		return err
	}
	if err := result.Err(); err != nil {
		return err
	}
	directory, err := os.MkdirTemp("", "seagull-generated-")
	if err != nil {
		return err
	}
	defer os.RemoveAll(directory)
	if err := seagull.WriteFiles(directory, result); err != nil {
		return err
	}
	fmt.Printf("generated %d queries\n", result.QueryCount)

Vet and Generate return an operational error separately from SQL diagnostics. Check report.Err() and result.Err() before writing the output too.

WriteFiles replaces files named by the result and removes stale files carrying Seagull's generated header. The temporary destination keeps this lesson's output separate from the application.

Step 2: Run it

go run .

generated 8 queries

The tool generated the eight queries you added in the first six lessons. Its supplied test runs the same workflow:

go test . -count=1

Step 3: Observe a diagnostic

Temporarily introduce a syntax error in the practice application's query file:

python3 - <<'PYTHON'
from pathlib import Path
path = Path("../01_first_query/db/queries/tasks.sql")
text = path.read_text()
path.write_text(text.replace("SELECT id, title, completed", "SELEC id, title, completed"))
PYTHON
go run .

The tool stops at the SQL diagnostic:

Q010

Restore the query and run again:

python3 - <<'PYTHON'
from pathlib import Path
path = Path("../01_first_query/db/queries/tasks.sql")
text = path.read_text()
path.write_text(text.replace("SELEC id, title, completed", "SELECT id, title, completed"))
PYTHON
go run .

generated 8 queries

For an application tool, continue with generate from Go, custom schema sources or the generator API.