Add ability to generate if-else blocks

[filiph]

A previous version had .asIf() for building statements like

if (something) {
  // ...
}

As far as I know, the only way to do these with current API is to write this manually via Code(...).

[matanlurey]

The problem with builders for statements is there are so many, and it is hard to cover everything.

Happy to accept PRs though for statements you feel add value!

[filiph]

Hmm, good point.

Maybe there a way to just let folks built their own statements (like the one above) in a safer way than right now?

Right now, I do something like this:

final conditionString = condition.accept(_dartEmitter).toString();
final returnStatement = literal(returnValue).returned.statement;
final returnString = returnStatement.accept(_dartEmitter).toString();
return Code('if ($conditionString) { $returnString }');

(_dartEmitter is a private member of a class that does not end up building the final code, so it seems a bit out of place here.)

Would it be better to have something like:

final buf = CodeBuffer()
  ..addString('if (')
  ..addExpression(condition)
  ..addString(') {')
  ..addStatement(literal(returnValue).returned)
  ..addString('}');
return buf.build();

Eh. Not sure if this is any better. What I was driving at is a way not to use DartEmitter until the last step. To keep the expressions and statements in their semantic form (as opposed to a string) as long as possible, and yet have the flexibility to just write stuff directly.

[eredo]

Just came across this issue and I was thinking about something like this:

CompountStatementBuilder()
  ..addStatement(refer('myBool').eq(literal('1')).asIf())
  ..addBlock(BlockBuilder()
    ..addStatement(literal(returnValue).returned.statement)
  )
  ..followedBy(CompountStatementBuilder()
    ..addStatement(literalElse)
    ..addBlock(/* .. */));

CompountStatementBuilder()
  ..addStatement(refer('myArray').asFor(refer('item')))
  ..addBlock(/* .. */);

CompountStatementBuilder()
  ..addStatement(literalTry)
  ..addBlock(/* .. */)
  // Maybe use builder callback directly for ease of use?
  ..followedBy((b) => b
    ..addStatement(literalCatch)
    ..addBlock(/* .. */));

Happy to setup a PR.

[TekExplorer]

I created a helper method like so:

Block ifStatement(
  Expression conditional,
  Code body, [
  bool singleLine = false,
]) =>
    Block.of([
      Code('if ('),
      conditional.code,
      Code(') {'),
      body,
      Code('}'),
    ]);

I even have one for try catch thats a bit more complicated

Block tryStatement({
  required Code try$,
  List<CatchClause> clauses = const [],
  Catch? catch$,
  Code? finally$,
}) {
  if (clauses.isEmpty && catch$ == null && finally$ == null) {
    throw ArgumentError(
        r'Must provide at least one clause such as in `clauses`, `catch$`, or `finally$`');
  }
  return Block((b) {
    b.statements.add(Code('try {'));
    b.statements.add(try$);
    b.statements.add(Code('}'));

    // on X {}

    // on X catch (e) {}
    // on X catch (e, s) {}

    // catch (e) {}
    // catch (e, s) {}
    for (final clause in clauses) {
      if (clause.on case final on) {
        b.statements.add(Code('on '));
        b.statements.add(on.code);
      }
      if (clause.catch$) {
        b.statements.add(Code('catch (e, s)'));
      }
      b.statements.add(Code('{'));
      b.statements.add(clause.body(refer('e'), refer('s')));
      b.statements.add(Code('}'));
    }

    if (catch$ != null) {
      b.statements.add(Code('catch (e, s) {'));
      b.statements.add(catch$.body(refer('e'), refer('s')));
      b.statements.add(Code('}'));
    }

    if (finally$ != null) {
      b.statements.add(Code('finally {'));
      b.statements.add(finally$);
      b.statements.add(Code('}'));
    }
  });
}

class CatchClause {
  final CatchBodyBuilder body;

  final Reference on;
  final bool catch$;

  CatchClause(
    Code body, {
    required this.on,
  })  : catch$ = false,
        body = ((_, __) => body);

  const CatchClause.catch$(
    this.body, {
    required this.on,
  }) : catch$ = true;
}

class Catch {
  final CatchBodyBuilder body;
  const Catch(this.body);

  static const rethrow$ = Catch(_rethrowBody);
  static Code _rethrowBody(_, __) => refer('rethrow').statement;
}

typedef CatchBodyBuilder = Code Function(Reference error, Reference stackTrace);

(note, i did not implement an option that excludes the stacktrace option) I believe that both statements need to exist in code_builder in some form, not necessarily like this.