Loop Variable Update

[robcxyz]

Loop Variable Update

Improve the loop parsing logic to allow declaring variables, ie i in a_list.

• Proposal Status: implemented

• Issue Number: 234

• Proposal Doc: loop-variable-update.md

Overview

Currently the loop logic inserts temporary variables item and index into the context so that they are available for rendering but this results in overlapping variables in embedded loops. What would be better is if we supported inserting the variable as part of the for key with var_name in a_list and similar semantics. Would require overhauling the parser some custom tokenizer.

Examples

Current - Still Supported

bars:

  - baz

  - bing

foo:

  ->: print {{item}}

  for: bars  

Future

Via Macros

Compact expression pre macro

bars:

  - baz

  - bing

foo:

  ->: print {{bar}}

  for: bar in bars  

Expanded post macro with new keys

bars:

  - baz

  - bing

foo:

  ->: print {{bar}}

  for:

    item: bar

    items:

      ... # Some list or string reference to a list

Pros:

• Explicit

Cons:

• Need to build additional interface to support item

Regex Parsing

Pseudo Code

def do(for_string: str):

    split_for = for_string.split(' in ')

    if len(split_for) == 2:

        for_var = split_for[0]

        # Put that var in tmp context

        loop_items = split_for[1]

    elif len(split_for) == 1:

        for_var = 'item'

        loop_items = split_for[0]

    else:

        raise

    # Then do normal stuff

Pros:

• Easy...

Cons:

• None - Will be replaced later when parser comes in

a:

  b: 1

  c: 2

  d: 3



e->: var {{item}} --for k, v in a

e:

  b: 1

  c: 2

  d: 3