Clojurians Log v2
yamlscript
I've been musing on what makes YAML a pretty good data syntax to write a programming language like YS in... When I started this project, my hopes for YAML being a reasonable syntax were pretty low. I started porting Clojure code to various made up YAML forms to see what I liked and what I didn't. To my pleasant surprise, it started looking pretty good. I've being thinking... could something similar be done in JSON, EDN or something else? If it came down to one thing, I'd give credit to YAML's "plain scalars" (unquoted strings), and the ability to use them vs the other scalar styles (quoted and literal). No other plain text data language that I know of has this (unquoted strings). To go a bit further, 3 of the other 4 scalar styles (single quoted, double quoted, and literal (heredoc semantics) play a big part in the language. Various scalar styles with various (code mode) semantics...
say: hello # hello is a symbol here
say: 'hello'
say: "hello $name"
say: |
hello $name,
How are you?
Suppose I have a block of cloudformation configuration that I want to template, which contains a variable expansion such as ${ENV} that I want to expand, is there a way to do this in Yamlscript? Could I perhaps drop into code mode in the middle of my data here?
--- !yamlscript/v0/
&cloudformationBlock
dataStream:
Type: AWS::Kinesis::Stream
Properties:
Name: ${ENV}_DATA_STREAM
RetentionPeriodHours: 24
ShardCount: 1
--- !yamlscript/v0
defn main():
ENV =: 'dev'
say: *cloudformationBlocksec
There are many ways to do this with YS. Here's one: cf.ys:
--- !yamlscript/v0/
=>:
ENV =: 'dev'
dataStream:
Type: AWS::Kinesis::Stream
Properties:
Name:: "$(=> ENV)_DATA_STREAM"
RetentionPeriodHours: 24
ShardCount: 1ys -Y cf.ys > cf.yamldataStream:
Type: AWS::Kinesis::Stream
Properties:
Name: dev_DATA_STREAM
RetentionPeriodHours: 24
ShardCount: 1note that "$(=> ENV)_DATA_STREAM" can be "${ENV}_DATA_STREAM" in 0.1.59 when that drops
code already in main
Here's slightly different approach that you might like better: cf.ys:
--- !yamlscript/v0/
=>:
data =: load('vars.yaml')
dataStream:
Type: AWS::Kinesis::Stream
Properties:
Name:: "$(data.ENV)_DATA_STREAM"
RetentionPeriodHours: 24
ShardCount: 1ENV: devdoes same thing
This is really great!
or... cf.ys:
--- !yamlscript/v0/
dataStream:
Type: AWS::Kinesis::Stream
Properties:
Name:: "$(ENV.'MY_ENV_LEVEL')_DATA_STREAM"
RetentionPeriodHours: 24
ShardCount: 1MY_ENV_LEVEL=dev ys -Y cf.ys > cf.yaml🙂
for completeness, you can put vars in a previous document in the same file and access them with $$:
cf.ys:
---
level: dev
--- !yamlscript/v0/
dataStream:
Type: AWS::Kinesis::Stream
Properties:
Name:: "$($$.level)_DATA_STREAM"
RetentionPeriodHours: 24
ShardCount: 1I was a bit confused at first because you named your var ENV which is a global mapping variable containing the environment in YS...
Also I doubt Name: dev_DATA_STREAM is the end result you would want,
but now you know some ways to get whatever it is you want.
I haven't used cloudformation but it's on my list to show how YS can help it.
Let me know if you need more help.
Thanks!
Also look at https://github.com/BetterThanTomorrow/calva/pull/2511
it's a complete YS refactoring of a 650 line circleci yaml file, that turned out really well
This is motivated by my interest in alternatives to the Serverless framework
URL?
https://www.serverless.com is going to change with v4.0 and will begin charging money it seems
I see
I imagine that many people & companies will be interested in alternatives to the Serverless framework
never heard of it until now
It’s pretty popular but there are some things that it’s not very good at, like as a small example you have to use a plugin to get if/then/else in your Serverless yaml
Cloudformation compiled with yamlscript would be like totally free to do programmatic things