feat: support AS pipe operator

ast/ast.go

@@ -154,6 +154,7 @@ type PipeOperator interface {
 
 func (PipeSelect) isPipeOperator() {}
 func (PipeWhere) isPipeOperator()  {}
+func (PipeAs) isPipeOperator()     {}
 
 // SelectItem represents expression in SELECT clause result columns list.
 type SelectItem interface {
@@ -1164,6 +1165,17 @@ type PipeWhere struct {
 	Expr Expr
 }
 
+// PipeAs is AS pipe operator node.
+//
+//	|> AS {{.Alias | sql}}
+type PipeAs struct {
+	// pos = Pipe
+	// end = Alias.end
+
+	Pipe  token.Pos // position of "|>"
+	Alias *Ident
+}
+
 // ================================================================================
 //
 // JOIN

ast/sql.go

@@ -330,6 +330,8 @@ func (p *PipeWhere) SQL() string {
 	return "|> WHERE " + p.Expr.SQL()
 }
 
+func (p *PipeAs) SQL() string { return "|> AS " + p.Alias.SQL() }
+
 // ================================================================================
 //
 // JOIN

parser.go

@@ -428,6 +428,9 @@ func (p *Parser) parsePipeOperator() ast.PipeOperator {
 			Pipe: pos,
 			Expr: expr,
 		}
+	case "AS":
+		p.nextToken()
+		return &ast.PipeAs{Pipe: pos, Alias: p.parseIdent()}
 	default:
 		panic(p.errorfAtToken(&p.Token, "expected pipe operator name, but: %q", p.Token.AsString))
 	}

testdata/input/query/pipe_as.sql

@@ -0,0 +1,3 @@
+FROM Singers
+|> AS s
+|> WHERE s.FirstName = "John"

testdata/result/query/pipe_as.sql.txt

@@ -0,0 +1,59 @@
+--- pipe_as.sql
+FROM Singers
+|> AS s
+|> WHERE s.FirstName = "John"
+
+--- AST
+&ast.QueryStatement{
+  Query: &ast.Query{
+    Query: &ast.FromQuery{
+      From: &ast.From{
+        Source: &ast.TableName{
+          Table: &ast.Ident{
+            NamePos: 5,
+            NameEnd: 12,
+            Name:    "Singers",
+          },
+        },
+      },
+    },
+    PipeOperators: []ast.PipeOperator{
+      &ast.PipeAs{
+        Pipe:  13,
+        Alias: &ast.Ident{
+          NamePos: 19,
+          NameEnd: 20,
+          Name:    "s",
+        },
+      },
+      &ast.PipeWhere{
+        Pipe: 21,
+        Expr: &ast.BinaryExpr{
+          Op:   "=",
+          Left: &ast.Path{
+            Idents: []*ast.Ident{
+              &ast.Ident{
+                NamePos: 30,
+                NameEnd: 31,
+                Name:    "s",
+              },
+              &ast.Ident{
+                NamePos: 32,
+                NameEnd: 41,
+                Name:    "FirstName",
+              },
+            },
+          },
+          Right: &ast.StringLiteral{
+            ValuePos: 44,
+            ValueEnd: 50,
+            Value:    "John",
+          },
+        },
+      },
+    },
+  },
+}
+
+--- SQL
+FROM Singers |> AS s |> WHERE s.FirstName = "John"

testdata/result/statement/pipe_as.sql.txt

@@ -0,0 +1,59 @@
+--- pipe_as.sql
+FROM Singers
+|> AS s
+|> WHERE s.FirstName = "John"
+
+--- AST
+&ast.QueryStatement{
+  Query: &ast.Query{
+    Query: &ast.FromQuery{
+      From: &ast.From{
+        Source: &ast.TableName{
+          Table: &ast.Ident{
+            NamePos: 5,
+            NameEnd: 12,
+            Name:    "Singers",
+          },
+        },
+      },
+    },
+    PipeOperators: []ast.PipeOperator{
+      &ast.PipeAs{
+        Pipe:  13,
+        Alias: &ast.Ident{
+          NamePos: 19,
+          NameEnd: 20,
+          Name:    "s",
+        },
+      },
+      &ast.PipeWhere{
+        Pipe: 21,
+        Expr: &ast.BinaryExpr{
+          Op:   "=",
+          Left: &ast.Path{
+            Idents: []*ast.Ident{
+              &ast.Ident{
+                NamePos: 30,
+                NameEnd: 31,
+                Name:    "s",
+              },
+              &ast.Ident{
+                NamePos: 32,
+                NameEnd: 41,
+                Name:    "FirstName",
+              },
+            },
+          },
+          Right: &ast.StringLiteral{
+            ValuePos: 44,
+            ValueEnd: 50,
+            Value:    "John",
+          },
+        },
+      },
+    },
+  },
+}
+
+--- SQL
+FROM Singers |> AS s |> WHERE s.FirstName = "John"