Add common functions for repositories (pgx and sql)

Author: hlubek

.github/workflows/test.yml

@@ -26,7 +26,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [ '1.20' ]
+        go-version: [ '1.20', '1.21' ]
         platform: [ 'ubuntu-latest' ]
     runs-on: ${{ matrix.platform }}
     steps:

README.md

@@ -14,6 +14,7 @@ This is a code generator to generate a bunch of structs and functions to impleme
 
 * Selecting JSON from the database allows for nested data and does most of the work that an ORM does on the read side. It can be used to flexibly load related data in an eager way (see [example](./example/pgx/repository/repository_project.go)).
 * Querying the database without too much abstraction gives a lot of flexibility - where needed.
+  Construct is paired with [github.com/networkteam/qrb](https://github.com/networkteam/qrb) as a PostgreSQL focused query builder that supports querying JSON. 
 * Not using the model itself for writes reduces a lot of complexity around dirty checking and other ORM features.
   It works well in an [CQRS](https://martinfowler.com/bliki/CQRS.html) architecture where commands and queries are separated.
 * Database migrations often need more thought and are outside the scope of this tool. 
@@ -113,112 +114,70 @@ Construct will automatically generate identifier expressions of fields (read col
 and a default `json_build_object` expression to select a model via JSON. This can be further modified to add additional properties. 
 
 *repository/customer_repository.go*
+
 ```go
 package repository
 
 import (
-	"context"
+  "context"
 
-	"github.com/gofrs/uuid"
-	"github.com/jackc/pgx/v5"
-	"github.com/networkteam/qrb"
-	"github.com/networkteam/qrb/builder"
-	"github.com/networkteam/qrb/fn"
-	"github.com/networkteam/qrb/qrbpgx"
+  "github.com/gofrs/uuid"
+  "github.com/jackc/pgx/v5"
+  "github.com/networkteam/construct/v2/constructpgx"
+  "github.com/networkteam/qrb"
+  "github.com/networkteam/qrb/builder"
+  "github.com/networkteam/qrb/fn"
+  "github.com/networkteam/qrb/qrbpgx"
 
-	".../myproject/model"
+  ".../myproject/model"
 )
 
 func FindCustomerByID(ctx context.Context, executor qrbpgx.Executor, id uuid.UUID) (model.Customer, error) {
-	q := qrb.
-		Select(customerJson()).
-		// A schema type for read columns (and the table) is generated as qrb identifier expressions by construct
-		From(customer).
-		LeftJoin(project).On(project.CustomerID.Eq(customer.ID)).
-		Where(customer.ID.Eq(qrb.Arg(id))).
-		GroupBy(customer.ID)
-
-	row, err := qrbpgx.Build(q).WithExecutor(executor).QueryRow(ctx)
-	if err != nil {
-		return result, err
-	}
-	return pgxScanRow[model.Customer](row)
+  q := qrb.
+    Select(customerJson()).
+    // A schema type for read columns (and the table) is generated as qrb identifier expressions by construct
+    From(customer).
+    LeftJoin(project).On(project.CustomerID.Eq(customer.ID)).
+    Where(customer.ID.Eq(qrb.Arg(id))).
+    GroupBy(customer.ID)
+
+  row, err := qrbpgx.Build(q).WithExecutor(executor).QueryRow(ctx)
+  if err != nil {
+    return result, err
+  }
+  return constructpgx.ScanRow[model.Customer](row)
 }
 
 // CustomerChangeSet is generated by construct for handling partially filled models
 func InsertCustomer(ctx context.Context, executor qrbpgx.Executor, changeSet CustomerChangeSet) error {
-	q := qrb.
-		InsertInto(customer).
-		// toMap is generated by construct 
-		SetMap(changeSet.toMap())
+  q := qrb.
+    InsertInto(customer).
+    // toMap is generated by construct 
+    SetMap(changeSet.toMap())
 
-	_, err := qrbpgx.Build(q).WithExecutor(executor).Exec(ctx)
-	return err
+  _, err := qrbpgx.Build(q).WithExecutor(executor).Exec(ctx)
+  return err
 }
 
 func UpdateCustomer(ctx context.Context, executor qrbpgx.Executor, id uuid.UUID, changeSet CustomerChangeSet) error {
-	q := qrb.
-		Update(customer).
-		Where(customer.ID.Eq(qrb.Arg(id))).
-		SetMap(changeSet.toMap())
+  q := qrb.
+    Update(customer).
+    Where(customer.ID.Eq(qrb.Arg(id))).
+    SetMap(changeSet.toMap())
 
-	res, err := qrbpgx.Build(q).WithExecutor(executor).Exec(ctx)
-	if err != nil {
-		return err
-	}
+  res, err := qrbpgx.Build(q).WithExecutor(executor).Exec(ctx)
+  if err != nil {
+    return err
+  }
 
-	return assertRowsAffected(res, "update", 1)
+  return constructpgx.AssertRowsAffected(res, "update", 1)
 }
 
 func customerJson() builder.JsonBuildObjectBuilder {
-	// customerDefaultJson is generated by construct and is a JsonBuildObjectBuilder that can be further modified (immutable)
-	return customerDefaultJson.
-		// It's easy to set additional properties
-		Prop("ProjectCount", qrb.Count(project.ID))
-}
-```
-
-These are common functions that can be shared by all repository implementations:
-
-*repository/commong.go*
-```go
-package repository
-
-import (
-	"fmt"
-
-	"github.com/jackc/pgx/v5"
-	"github.com/jackc/pgx/v5/pgconn"
-
-	"github.com/networkteam/construct/v2"
-)
-
-func pgxCollectRow[T any](row pgx.CollectableRow) (T, error) {
-	return pgxScanRow[T](row)
-}
-
-func pgxScanRow[T any](row pgx.Row) (T, error) {
-	var result T
-	err := row.Scan(&result)
-	if err != nil {
-		return result, fmt.Errorf("scanning row: %w", pgxToConstructErr(err))
-	}
-	return result, nil
-}
-
-func pgxToConstructErr(err error) error {
-	if err == pgx.ErrNoRows {
-		return construct.ErrNotFound
-	}
-	return err
-}
-
-func assertRowsAffected(res pgconn.CommandTag, op string, numberOfRows int64) error {
-	rowsAffected := res.RowsAffected()
-	if rowsAffected != numberOfRows {
-		return fmt.Errorf("%s affected %d rows, but expected exactly %d", op, rowsAffected, numberOfRows)
-	}
-	return nil
+  // customerDefaultJson is generated by construct and is a JsonBuildObjectBuilder that can be further modified (immutable)
+  return customerDefaultJson.
+    // It's easy to set additional properties
+    Prop("ProjectCount", qrb.Count(project.ID))
 }
 ```
 

constructpgx/constructpgx.go

@@ -0,0 +1,73 @@
+package constructpgx
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+
+	"github.com/networkteam/construct/v2"
+)
+
+// CollectRows collects all rows to the given target type from a ExecutiveQueryBuilder.Query result.
+// It is based on pgx.CollectRows but accepts an additional error for easier use.
+func CollectRows[T any](rows pgx.Rows, err error) ([]T, error) {
+	if err != nil {
+		return nil, err
+	}
+
+	defer rows.Close()
+
+	slice := []T{}
+
+	for rows.Next() {
+		value, err := scanRow[T](rows)
+		if err != nil {
+			return nil, err
+		}
+		slice = append(slice, value)
+	}
+
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	return slice, nil
+}
+
+func pgxToConstructErr(err error) error {
+	if errors.Is(err, pgx.ErrNoRows) {
+		return construct.ErrNotFound
+	}
+	return err
+}
+
+// ScanRow scans a single row to the given target type from a ExecutiveQueryBuilder.QueryRow result.
+func ScanRow[T any](row pgx.Row, err error) (T, error) {
+	var result T
+	if err != nil {
+		return result, pgxToConstructErr(err)
+	}
+	return scanRow[T](row)
+}
+
+func scanRow[T any](row pgx.Row) (T, error) {
+	var result T
+	err := row.Scan(&result)
+	if err != nil {
+		return result, fmt.Errorf("scanning row: %w", pgxToConstructErr(err))
+	}
+	return result, nil
+}
+
+// AssertRowsAffected checks if the given result affected exactly the expected number of rows.
+func AssertRowsAffected(result pgconn.CommandTag, operation string, expectedRows int) error {
+	actualRows := result.RowsAffected()
+	if actualRows != int64(expectedRows) {
+		return fmt.Errorf("%s affected %d rows, but expected exactly %d", operation, actualRows, expectedRows)
+	}
+
+	return nil
+
+}

constructpgx/constructpgx_test.go

@@ -0,0 +1,99 @@
+package constructpgx_test
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/networkteam/construct/v2"
+	"github.com/networkteam/construct/v2/constructpgx"
+)
+
+type user struct {
+	ID   int
+	Name string
+}
+
+type mockRow struct {
+	scanUser *user
+	scanErr  error
+}
+
+func (r *mockRow) Scan(dest ...any) error {
+	if r.scanErr != nil {
+		return r.scanErr
+	}
+
+	if len(dest) != 1 {
+		return errors.New("mockRow.Scan: dest must have length 1")
+	}
+
+	if r.scanUser == nil {
+		return errors.New("mockRow.Scan: scanUser is nil")
+	}
+
+	*dest[0].(*user) = *r.scanUser
+
+	return nil
+}
+
+func TestScanRow(t *testing.T) {
+	t.Run("scans row without error", func(t *testing.T) {
+		row := mockRow{
+			scanUser: &user{ID: 1, Name: "test"},
+		}
+		record, err := constructpgx.ScanRow[user](&row, nil)
+		require.NoError(t, err)
+
+		assert.Equal(t, user{ID: 1, Name: "test"}, record)
+	})
+
+	t.Run("returns QueryRow error", func(t *testing.T) {
+		row := mockRow{}
+		queryRowErr := errors.New("some query error")
+		_, err := constructpgx.ScanRow[user](&row, queryRowErr)
+		require.ErrorIs(t, err, queryRowErr)
+	})
+
+	t.Run("returns Scan error", func(t *testing.T) {
+		scanErr := errors.New("some scan error")
+		row := mockRow{
+			scanErr: scanErr,
+		}
+		_, err := constructpgx.ScanRow[user](&row, nil)
+		require.ErrorIs(t, err, scanErr)
+	})
+
+	t.Run("converts Scan err to ErrNotFound", func(t *testing.T) {
+		scanErr := pgx.ErrNoRows
+		row := mockRow{
+			scanErr: scanErr,
+		}
+		_, err := constructpgx.ScanRow[user](&row, nil)
+		require.ErrorIs(t, err, construct.ErrNotFound)
+	})
+
+	t.Run("converts QueryRow err to ErrNotFound", func(t *testing.T) {
+		// Note: the underlying error usually only occurs during Scan, but we want to make sure it works here as well.
+		queryRowErr := pgx.ErrNoRows
+		row := mockRow{}
+		_, err := constructpgx.ScanRow[user](&row, queryRowErr)
+		require.ErrorIs(t, err, construct.ErrNotFound)
+	})
+}
+
+func TestAssertRowsAffected(t *testing.T) {
+	t.Run("returns nil if rows affected matches expected", func(t *testing.T) {
+		err := constructpgx.AssertRowsAffected(pgconn.NewCommandTag("UPDATE 2"), "update", 2)
+		require.NoError(t, err)
+	})
+
+	t.Run("returns error if rows affected does not match expected", func(t *testing.T) {
+		err := constructpgx.AssertRowsAffected(pgconn.NewCommandTag("UPDATE 2"), "update", 1)
+		require.Error(t, err)
+	})
+}