0.9.0 proposal: Cleaning up Yaml DSL - devassistant (INACTIVE) - Fedora mailing-lists

10 Feb 2014


      So, I've been talking to people who actually tried to use DevAssistant and based on their and my own experience, I'd like to propose that we clean up the Yaml DSL (and extend it in a certain way). Here's the proposal that I've put together:
Current Problems
================
- assigning a literal string value much easier
- assigning a result of expression/section much easier
- more consistent (explicit usage of either literals or expressions for assignments and command runners)
What the Solution Looks Like
============================
This is just an example, move down to see new "walkthrough" that'll guide you through some terminology and how it all works.
run:
- foo: bar # command runner gets literal value
- foo~: $eval and $this # command runner gets expression result
- foo: ~$eval and $this # command runner gets expression result
# some more complicated stuff
- $newdict:
    foo: literal
    bar: [another, literal]
    $eggs~: $eval and $this
    pwd~:
    - ask_password: something
    spam:
    - literal
    - literal
    - ~$eval and $this
- some_command_runner:
  - ~$eval and $this
  - literal
  - - literal
    - ~$eval and $this
  - - foo~: $eval and $this
    - bah: ~$bar and $baz
  - spam~: $eval and $this
  - spam: dont eval this
run, if/else, for are exceptions - they're execution sections without "~".
Proposed "Walkthrough"
======================
Run is an *execution section* - it consists of an *expression* or a list of *commands*. Expressions consist of variables, brackets and logical keywords, variables start with dollar sign.
Example of an expression:
($foo and $bar) or $baz
In command list, every command is made up of *command type* and *command input*:
- command_type: command_input
- another_command: another_input
Each execution section returns two values - *logical result* (True/False - e.g. success/failure) and *result* (e.g. a return value). Logical result and result of expression is determined by (link to expression rules), logical result and result of a command list are that of the last command. Every command type specifies these differently, see (link).
There are two types of command input - *literal input* and *execution input*.
- Execution input makes DA run the input as an execution section and return its logical result and result.
- Literal input returns a literal value and its logical result (False if empty string/list/mapping, True otherwise).
Literal input is implicit, execution input is triggered by appending "~" at the end of command type. A string can also be made execution input (=> expression) by prepending "~".
- comm_type: literal_input
- comm_type2:
  - some
  - structured
  - literal
  - input
- comm_type3~: $execute or $this
- comm_type4~:
  - this: is a short run section
  - with: some commands
Please send your comments/concerns/ideas.
Slavek.