I've done some further exploring. The expression computed by the line https://github.com/MarkNahabedian/Goshua/blob/ee72218487f39d2e97ade086df23dbcfcb4c2db3/rete/rule_compiler/rule_compiler.go#L214 has both a valid Pos() and a valid End(). parseExpression is defined at https://github.com/MarkNahabedian/Goshua/blob/ee72218487f39d2e97ade086df23dbcfcb4c2db3/rete/rule_compiler/ast_helpers.go#L12 It just panic-guards a call to parser.ParseExpr. ParseExpr does not take a File or FileSet as argument, so how can the expression it returns have valid Pos values?
I believe these Pos values are being misinterpreted by printer.indentList (defined at line 1085 of https://golang.org/src/go/printer/nodes.go) and causing it to iintroduce spurious newlines. After many hours of mindless coding I now have a function that will strip Pos information from an ast. When parseExpression uses that function on its results the spuriouys newline probem goes away. I'm convinced that the ast returned by parser.ParseExpr should not contain any Pos values since they can't possibly be meaningful. On Wednesday, July 4, 2018 at 6:38:44 PM UTC-4, Mark Nahabedian wrote: > > I'm using go/ast and friends to generate go code. I'm having trouble > with spurious newlines being added to the output. These cause the > compiler to balk. > > For broader context, my code can be found at > > https://github.com/MarkNahabedian/Goshua/tree/master/rete/rule_compiler/rule_compiler.go > . > > The point of the code below is to build a map from strings that are > the names of go types to a function that returns true when invoked on > an object of that type. This because I've not found a way to use > types as first class objects. > > // line 214 > e := parseExpression(fmt.Sprintf( > `rete.EnsureTypeTestRegistered("%s", func(i interface{}) bool { _, ok := > i.(%s); return ok })`, > pType, pType)) > initFunc.Body.List = append(initFunc.Body.List, > &ast.ExprStmt{ X: e}) > > // line 221 > newAstFile.Decls = append(newAstFile.Decls, initFunc) > > // line 224 > writeFile(fset, newAstFile, outname) > > > parseExpression is defined in ast_helpers.go. It calls > parser.ParseExpr and panics if there'sd an error. > > writeFile is defined in utils.go. It calls format.Node to > serialize the generated source code. > > > Here is some sample output that illustrates the problem I'm observing. > Note that the spurious whitespace is not added consistently. Two of > these three return statements get the error "not enough arguments to > return" which go away if the extra newlines are removed. > > rete.EnsureTypeTestRegistered("Couple", func(i interface{}) bool { > _, ok := i.(Couple) > return > > ok > }) > rete.EnsureTypeTestRegistered("FaceToFace", func(i interface{}) bool { > _, > ok := i.(FaceToFace) > return ok > }) > rete.EnsureTypeTestRegistered("Tandem", func(i interface{}) bool { > _, ok := i.(Tandem) > return > > ok > }) > > Also observe that in the middle case spurious whitespace is added to > the assignment/declaration statement rather that the return statement. > > Why is this happening and how do I prevent it? > > Thanks. > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
