Implement support for enum ordering

internal/endtoend/testdata/enum_ordering/postgresql/stdlib/query.sql

@@ -0,0 +1,2 @@
+-- name: GetAll :many
+SELECT * FROM foo;

internal/endtoend/testdata/enum_ordering/postgresql/stdlib/schema.sql

@@ -0,0 +1,11 @@
+CREATE TYPE enum_type AS ENUM ('first', 'last');
+ALTER TYPE enum_type ADD VALUE 'afterlast' AFTER 'last';
+ALTER TYPE enum_type ADD VALUE 'third' AFTER 'first';
+ALTER TYPE enum_type ADD VALUE 'fourth' BEFORE 'last';
+ALTER TYPE enum_type ADD VALUE 'fifth' AFTER 'fourth';
+ALTER TYPE enum_type ADD VALUE 'second' BEFORE 'third';
+ALTER TYPE enum_type ADD VALUE 'beforefirst' BEFORE 'first';
+
+CREATE TABLE foo (
+    id SERIAL PRIMARY KEY
+);

internal/endtoend/testdata/enum_ordering/postgresql/stdlib/sqlc.json

@@ -0,0 +1,19 @@
+{
+  "version": "2",
+  "sql": [
+    {
+      "engine": "postgresql",
+      "schema": "schema.sql",
+      "queries": "query.sql",
+      "gen": {
+        "go": {
+          "out" : "go",
+          "package" : "db",
+          "emit_interface": true,
+          "emit_all_enum_values": true,
+          "emit_enum_valid_method": true
+        }
+      }
+    }
+  ]
+}

internal/engine/postgresql/parse.go

@@ -211,6 +211,9 @@ func translate(node *nodes.Node) (ast.Node, error) {
 			return &ast.AlterTypeAddValueStmt{
 				Type:               rel.TypeName(),
 				NewValue:           makeString(n.NewVal),
+				NewValHasNeighbor:  len(n.NewValNeighbor) > 0,
+				NewValNeighbor:     makeString(n.NewValNeighbor),
+				NewValIsAfter:      n.NewValIsAfter,
 				SkipIfNewValExists: n.SkipIfNewValExists,
 			}, nil
 		}

internal/sql/ast/alter_type_add_value_stmt.go

@@ -3,6 +3,9 @@ package ast
 type AlterTypeAddValueStmt struct {
 	Type               *TypeName
 	NewValue           *string
+	NewValHasNeighbor  bool
+	NewValNeighbor     *string
+	NewValIsAfter      bool
 	SkipIfNewValExists bool
 }
 

internal/sql/catalog/types.go

@@ -3,7 +3,6 @@ package catalog
 import (
 	"errors"
 	"fmt"
-
 	"github.com/kyleconroy/sqlc/internal/sql/ast"
 	"github.com/kyleconroy/sqlc/internal/sql/sqlerr"
 )
@@ -197,20 +196,47 @@ func (c *Catalog) alterTypeAddValue(stmt *ast.AlterTypeAddValueStmt) error {
 		return fmt.Errorf("type is not an enum: %T", stmt.Type)
 	}
 
-	newIndex := -1
+	existingIndex := -1
 	for i, val := range enum.Vals {
 		if val == *stmt.NewValue {
-			newIndex = i
+			existingIndex = i
 		}
 	}
-	if newIndex >= 0 {
+
+	if existingIndex >= 0 {
 		if !stmt.SkipIfNewValExists {
-			return fmt.Errorf("type %T already has value %s", stmt.Type, *stmt.NewValue)
+			return fmt.Errorf("enum %s already has value %s", enum.Name, *stmt.NewValue)
 		} else {
 			return nil
 		}
 	}
-	enum.Vals = append(enum.Vals, *stmt.NewValue)
+
+	if stmt.NewValHasNeighbor {
+		insertIndex := -1
+		for i, val := range enum.Vals {
+			if val == *stmt.NewValNeighbor {
+				if stmt.NewValIsAfter {
+					insertIndex = i + 1
+				} else {
+					insertIndex = i
+				}
+			}
+		}
+
+		if insertIndex == -1 {
+			return fmt.Errorf("enum %s unable to find existing neighbor value %s for new value %s", enum.Name, *stmt.NewValNeighbor, *stmt.NewValue)
+		}
+
+		if insertIndex == len(enum.Vals) {
+			enum.Vals = append(enum.Vals, *stmt.NewValue)
+		} else {
+			enum.Vals = append(enum.Vals[:insertIndex+1], enum.Vals[insertIndex:]...)
+			enum.Vals[insertIndex] = *stmt.NewValue
+		}
+	} else {
+		enum.Vals = append(enum.Vals, *stmt.NewValue)
+	}
+
 	return nil
 }