feat(errors): add unique constraint violation error

docs/pages/docs/reference/client/errors.md

@@ -0,0 +1,40 @@
+# Errors
+
+## ErrNotFound
+
+`ErrNotFound` is returned when a query does not return any results. This error may be returned in `FindUnique`, `FindFirst`, but also when updating or deleting single records using `FindUnique().Update()` and `FindUnique().Delete()`.
+
+```go
+post, err := client.Post.FindFirst(
+  db.Post.Title.Equals("hi"),
+).Exec(ctx)
+if err != nil {
+  if errors.Is(err, db.ErrNotFound) {
+    panic("no record with title 'hi' found")
+  }
+  panic("error occurred: %s", err)
+}
+```
+
+## IsUniqueConstraintViolation
+
+A unique constraint violation happens when a query attempts to insert or update a record with a value that already exists in the database, or in other words, violates a unique constraint.
+
+```go
+user, err := db.User.CreateOne(...).Exec(cxt)
+if err != nil {
+  if info, err := db.IsErrUniqueConstraint(err); err != nil {
+    // Fields exists for Postgres and SQLite
+    log.Printf("unique constraint on the fields: %s", info.Fields)
+
+    // you can also compare it with generated field names:
+    if info.Fields[0] == db.User.Name.Field() {
+      // do something
+      log.Printf("unique constraint on the `user.name` field")
+    }
+
+    // For MySQL and MongoDB, use the constraint key
+    log.Printf("unique constraint on the key: %s", info.Key)
+  }
+}
+```

engine/mock/do.go

@@ -5,7 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 
-	"github.com/steebchen/prisma-client-go/engine"
+	"github.com/steebchen/prisma-client-go/engine/protocol"
 )
 
 func (e *Engine) Do(_ context.Context, payload interface{}, v interface{}) error {
@@ -16,7 +16,7 @@ func (e *Engine) Do(_ context.Context, payload interface{}, v interface{}) error
 
 	n := -1
 	for i, e := range expectations {
-		req := payload.(engine.GQLRequest)
+		req := payload.(protocol.GQLRequest)
 		str, err := e.Query.Build()
 		if err != nil {
 			return err

engine/protocol.go → engine/protocol/protocol.go

@@ -1,4 +1,4 @@
-package engine
+package protocol
 
 import (
 	"encoding/json"
@@ -33,11 +33,30 @@ type GQLBatchRequest struct {
 	Transaction bool         `json:"transaction"`
 }
 
-// GQLError is a GraphQL Error
+type UserFacingError struct {
+	IsPanic   bool   `json:"is_panic"`
+	Message   string `json:"message"`
+	Meta      Meta   `json:"meta"`
+	ErrorCode string `json:"error_code"`
+}
+
+func (e *UserFacingError) Error() string {
+	return e.Message
+}
+
+type Meta struct {
+	Target interface{} `json:"target"` // can be of type []string or string
+}
+
+// GQLError is a GraphQL Message
 type GQLError struct {
-	Message    string                 `json:"error"` // note: the query-engine uses 'error' instead of 'message'
-	Path       []string               `json:"path"`
-	Extensions map[string]interface{} `json:"query"`
+	Message         string           `json:"error"`
+	UserFacingError *UserFacingError `json:"user_facing_error"`
+	Path            []string         `json:"path"`
+}
+
+func (e *GQLError) Error() string {
+	return e.Message
 }
 
 func (e *GQLError) RawMessage() string {

engine/proxy.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/steebchen/prisma-client-go/binaries"
+	"github.com/steebchen/prisma-client-go/engine/protocol"
 	"github.com/steebchen/prisma-client-go/logger"
 	"github.com/steebchen/prisma-client-go/runtime/types"
 )
@@ -108,7 +109,7 @@ func (e *DataProxyEngine) Do(ctx context.Context, payload interface{}, into inte
 
 	startParse := time.Now()
 
-	var response GQLResponse
+	var response protocol.GQLResponse
 	if err := json.Unmarshal(body, &response); err != nil {
 		return fmt.Errorf("json gql resopnse unmarshal: %w", err)
 	}

engine/request.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/steebchen/prisma-client-go/engine/protocol"
 	"github.com/steebchen/prisma-client-go/logger"
 	"github.com/steebchen/prisma-client-go/runtime/types"
 )
@@ -28,18 +29,23 @@ func (e *QueryEngine) Do(ctx context.Context, payload interface{}, v interface{}
 
 	startParse := time.Now()
 
-	var response GQLResponse
+	var response protocol.GQLResponse
 	if err := json.Unmarshal(body, &response); err != nil {
 		return fmt.Errorf("json gql response unmarshal: %w", err)
 	}
 
 	if len(response.Errors) > 0 {
-		first := response.Errors[0]
-		if first.RawMessage() == internalUpdateNotFoundMessage ||
-			first.RawMessage() == internalDeleteNotFoundMessage {
+		e := response.Errors[0]
+		if e.RawMessage() == internalUpdateNotFoundMessage ||
+			e.RawMessage() == internalDeleteNotFoundMessage {
 			return types.ErrNotFound
 		}
-		return fmt.Errorf("pql error: %s", first.RawMessage())
+
+		if e.UserFacingError != nil {
+			return fmt.Errorf("user facing error: %w", e.UserFacingError)
+		}
+
+		return fmt.Errorf("internal error: %s", e.RawMessage())
 	}
 
 	response.Data.Result, err = transformResponse(response.Data.Result)

generator/run.go

@@ -78,6 +78,7 @@ func generateClient(input *Root) error {
 		"client",
 		"enums",
 		"errors",
+		"fields",
 		"mock",
 		"models",
 		"query",

generator/templates/errors.gotpl

@@ -1 +1,29 @@
+{{- /*gotype:github.com/steebchen/prisma-client-go/generator.Root*/ -}}
+
 var ErrNotFound = types.ErrNotFound
+var IsErrNotFound = types.IsErrNotFound
+
+type ErrUniqueConstraint = types.ErrUniqueConstraint[prismaFields]
+
+// IsErrUniqueConstraint returns on a unique constraint error or violation with error info
+// Use as follows:
+//
+//	user, err := db.User.CreateOne(...).Exec(cxt)
+//	if err != nil {
+//		if info, err := db.IsErrUniqueConstraint(err); err != nil {
+//			// Fields exists for Postgres and SQLite
+//			log.Printf("unique constraint on the fields: %s", info.Fields)
+//
+//			// you can also compare it with generated field names:
+//			if info.Fields[0] == db.User.Name.Field() {
+//				// do something
+//			}
+//
+//			// For MySQL, use the constraint key
+//			log.Printf("unique constraint on the key: %s", info.Key)
+//		}
+//	}
+//
+func IsErrUniqueConstraint(err error) (*types.ErrUniqueConstraint[prismaFields], bool) {
+	return types.CheckUniqueConstraint[prismaFields](err)
+}

generator/templates/fields.gotpl

@@ -0,0 +1,11 @@
+{{- /*gotype:github.com/steebchen/prisma-client-go/generator.Root*/ -}}
+
+type prismaFields string
+
+{{ range $model := $.AST.Models }}
+	type {{ $model.Name.GoLowerCase }}PrismaFields = prismaFields
+
+	{{ range $field := $model.Fields }}
+		const {{ $model.Name.GoLowerCase }}Field{{ $field.Name.GoCase }} {{ $model.Name.GoLowerCase }}PrismaFields = "{{ $field.Name }}"
+	{{ end }}
+{{ end }}

generator/templates/query.gotpl

@@ -452,5 +452,10 @@
 				}
 			{{ end }}
 		{{ end }}
+
+		{{/* Returns static field names */}}
+		func (r {{ $struct }}) Field() {{ $model.Name.GoLowerCase }}PrismaFields {
+			return {{ $model.Name.GoLowerCase }}Field{{ $field.Name.GoCase }}
+		}
 	{{ end }}
 {{ end }}

go.mod

@@ -1,9 +1,15 @@
 module github.com/steebchen/prisma-client-go
 
-go 1.16
+go 1.18
 
 require (
 	github.com/joho/godotenv v1.5.1
 	github.com/shopspring/decimal v1.3.1
 	github.com/stretchr/testify v1.8.4
 )
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,4 +1,3 @@
-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/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
@@ -7,15 +6,9 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/shopspring/decimal v1.3.1 h1:2Usl1nmF/WZucqkFZhnfFYxxxu8LG21F6nPQBE5gKV8=
 github.com/shopspring/decimal v1.3.1/go.mod h1:DKyhrW/HYNuLGql+MJL6WCR6knT2jwCFRcu2hWCYk4o=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 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=

runtime/builder/builder.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/steebchen/prisma-client-go/engine"
+	"github.com/steebchen/prisma-client-go/engine/protocol"
 	"github.com/steebchen/prisma-client-go/logger"
 )
 
@@ -294,7 +295,7 @@ func (q Query) Exec(ctx context.Context, into interface{}) error {
 	if err != nil {
 		return err
 	}
-	payload := engine.GQLRequest{
+	payload := protocol.GQLRequest{
 		Query:     str,
 		Variables: map[string]interface{}{},
 	}

runtime/transaction/transaction.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/steebchen/prisma-client-go/engine"
+	"github.com/steebchen/prisma-client-go/engine/protocol"
 	"github.com/steebchen/prisma-client-go/runtime/builder"
 )
 
@@ -27,17 +28,17 @@ func (r TX) Transaction(queries ...Param) Exec {
 type Exec struct {
 	queries  []Param
 	engine   engine.Engine
-	requests []engine.GQLRequest
+	requests []protocol.GQLRequest
 }
 
 func (r Exec) Exec(ctx context.Context) error {
-	r.requests = make([]engine.GQLRequest, len(r.queries))
+	r.requests = make([]protocol.GQLRequest, len(r.queries))
 	for i, query := range r.queries {
 		str, err := query.ExtractQuery().Build()
 		if err != nil {
 			return err
 		}
-		r.requests[i] = engine.GQLRequest{
+		r.requests[i] = protocol.GQLRequest{
 			Query:     str,
 			Variables: map[string]interface{}{},
 		}
@@ -48,8 +49,8 @@ func (r Exec) Exec(ctx context.Context) error {
 		defer close(q.ExtractQuery().TxResult)
 	}
 
-	var result engine.GQLBatchResponse
-	payload := engine.GQLBatchRequest{
+	var result protocol.GQLBatchResponse
+	payload := protocol.GQLBatchRequest{
 		Batch:       r.requests,
 		Transaction: true,
 	}

runtime/types/errors.go

@@ -1,6 +1,69 @@
 package types
 
-import "errors"
+import (
+	"errors"
+
+	"github.com/steebchen/prisma-client-go/engine/protocol"
+)
 
 // ErrNotFound gets returned when a database record does not exist
 var ErrNotFound = errors.New("ErrNotFound")
+
+// IsErrNotFound is true if the error is a ErrNotFound, which gets returned when a database record does not exist
+// This can happen when you call `FindUnique` on a record, or update or delete a single record which doesn't exist.
+func IsErrNotFound(err error) bool {
+	return errors.Is(err, ErrNotFound)
+}
+
+type F interface {
+	~string
+}
+
+type ErrUniqueConstraint[T F] struct {
+	// Message is the error message
+	Message string
+	// Fields only shows on Postgres
+	Fields []T
+	// Key only shows on MySQL
+	Key string
+}
+
+// CheckUniqueConstraint returns on a unique constraint error or violation with error info
+// Ideally this will be replaced with Prisma-generated errors in the future
+func CheckUniqueConstraint[T F](err error) (*ErrUniqueConstraint[T], bool) {
+	if err == nil {
+		return nil, false
+	}
+
+	var ufr *protocol.UserFacingError
+	if ok := errors.As(err, &ufr); !ok {
+		return nil, false
+	}
+
+	if ufr.ErrorCode != "P2002" {
+		return nil, false
+	}
+
+	// postgres
+	if items, ok := ufr.Meta.Target.([]interface{}); ok {
+		var fields []T
+		for _, f := range items {
+			field, ok := f.(string)
+			if ok {
+				fields = append(fields, T(field))
+			}
+		}
+		return &ErrUniqueConstraint[T]{
+			Fields: fields,
+		}, true
+	}
+
+	// mysql
+	if item, ok := ufr.Meta.Target.(string); ok {
+		return &ErrUniqueConstraint[T]{
+			Key: item,
+		}, true
+	}
+
+	return nil, false
+}