dialect/entsql: add Skip annotation (#4156)

.golangci.yml

@@ -8,8 +8,8 @@ linters-settings:
   dupl:
     threshold: 100
   funlen:
-    lines: 140
-    statements: 140
+    lines: 200
+    statements: 200
   goheader:
     template: |-
       Copyright 2019-present Facebook Inc. All rights reserved.

dialect/entsql/annotation.go

@@ -149,6 +149,15 @@ type Annotation struct {
 	//	}
 	//
 	Checks map[string]string `json:"checks,omitempty"`
+
+	// Skip indicates that the field or the schema is skipped/ignored during
+	// migration (e.g., defined externally).
+	//
+	//	entsql.Annotation{
+	//		Skip: true,
+	//	}
+	//
+	Skip bool `json:"skip,omitempty"`
 }
 
 // Name describes the annotation name.
@@ -217,6 +226,12 @@ func Checks(c map[string]string) *Annotation {
 	}
 }
 
+// Skip indicates that the field or the schema is skipped/ignored during
+// migration (e.g., defined externally).
+func Skip() *Annotation {
+	return &Annotation{Skip: true}
+}
+
 // Default specifies a literal default value of a column. Note that using
 // this option overrides the default behavior of the code-generation.
 //
@@ -358,6 +373,9 @@ func (a Annotation) Merge(other schema.Annotation) schema.Annotation {
 			a.Checks[name] = check
 		}
 	}
+	if ant.Skip {
+		a.Skip = true
+	}
 	return a
 }
 

entc/gen/graph.go

@@ -623,11 +623,17 @@ func (g *Graph) Tables() (all []*schema.Table, err error) {
 		if n.HasOneFieldID() {
 			table.AddPrimary(n.ID.PK())
 		}
-		ant := n.EntSQL()
-		if ant != nil {
+		switch ant := n.EntSQL(); {
+		case ant == nil:
+		case ant.Skip:
+			continue
+		default:
 			table.SetAnnotation(ant).SetSchema(ant.Schema)
 		}
 		for _, f := range n.Fields {
+			if a := f.EntSQL(); a != nil && a.Skip {
+				continue
+			}
 			if !f.IsEdgeField() {
 				table.AddColumn(f.Column())
 			}