void visitIfElement()

in lib/src/source_visitor.dart [1898:2021]
67 lines of code
15 McCabe index (conditional complexity)

  void visitIfElement(IfElement node) {
    // Treat a chain of if-else elements as a single unit so that we don't
    // unnecessarily indent each subsequent section of the chain.
    var ifElements = [
      for (CollectionElement? thisNode = node;
          thisNode is IfElement;
          thisNode = thisNode.elseElement)
        thisNode
    ];

    // If the body of the then or else branch is a spread of a collection
    // literal, then we want to format those collections more like blocks than
    // like standalone objects. In particular, if both the then and else branch
    // are spread collection literals, we want to ensure that they both split
    // if either splits. So this:
    //
    //     [
    //       if (condition) ...[
    //         thenClause
    //       ] else ...[
    //         elseClause
    //       ]
    //     ]
    //
    // And not something like this:
    //
    //     [
    //       if (condition) ...[
    //         thenClause
    //       ] else ...[elseClause]
    //     ]
    //
    // To do that, if we see that either clause is a spread collection, we
    // create a single rule and force both collections to use it.
    var spreadRule = Rule();
    var spreadBrackets = <CollectionElement, Token>{};
    for (var element in ifElements) {
      var spreadBracket = _findSpreadCollectionBracket(element.thenElement);
      if (spreadBracket != null) {
        spreadBrackets[element] = spreadBracket;
        beforeBlock(spreadBracket, spreadRule, null);
      }
    }

    var elseSpreadBracket =
        _findSpreadCollectionBracket(ifElements.last.elseElement);
    if (elseSpreadBracket != null) {
      spreadBrackets[ifElements.last.elseElement!] = elseSpreadBracket;
      beforeBlock(elseSpreadBracket, spreadRule, null);
    }

    void visitChild(CollectionElement element, CollectionElement child) {
      builder.nestExpression(indent: 2, now: true);

      // Treat a spread of a collection literal like a block in an if statement
      // and don't split after the "else".
      var isSpread = spreadBrackets.containsKey(element);
      if (isSpread) {
        space();
      } else {
        split();

        // If the then clause is a non-spread collection or lambda, make sure the
        // body is indented.
        builder.startBlockArgumentNesting();
      }

      visit(child);

      if (!isSpread) builder.endBlockArgumentNesting();
      builder.unnest();
    }

    // Wrap the whole thing in a single rule. If a split happens inside the
    // condition or the then clause, we want the then and else clauses to split.
    builder.startLazyRule();

    var hasInnerControlFlow = false;
    for (var element in ifElements) {
      // The condition.
      token(element.ifKeyword);
      space();
      token(element.leftParenthesis);
      visit(element.condition);
      token(element.rightParenthesis);

      visitChild(element, element.thenElement);
      if (_isControlFlowElement(element.thenElement)) {
        hasInnerControlFlow = true;
      }

      // Handle this element's "else" keyword and prepare to write the element,
      // but don't write it. It will either be the next element in [ifElements]
      // or the final else element handled after the loop.
      if (element.elseElement != null) {
        if (spreadBrackets.containsKey(element)) {
          space();
        } else {
          split();
        }

        token(element.elseKeyword);

        // If there is another if element in the chain, put a space between
        // it and this "else".
        if (element != ifElements.last) space();
      }
    }

    // Handle the final trailing else if there is one.
    var lastElse = ifElements.last.elseElement;
    if (lastElse != null) {
      visitChild(lastElse, lastElse);

      if (_isControlFlowElement(lastElse)) {
        hasInnerControlFlow = true;
      }
    }

    // If a control flow element is nested inside another, force the outer one
    // to split.
    if (hasInnerControlFlow) builder.forceRules();
    builder.endRule();
  }