Move some of the caching logic (source file checksum) out of Starmelon
into a shared infra crate.
I have 4 similar tooling use cases for working with elm projects in
Rust.
1. Starmelon needs to create a modified copy of an existing elm
application with extra dependencies and source directories. The
extension elm application points to the source directories of the
parent
2. Elm reactor needs to compile an elm module into javascript with
caching.
3. SQL reactor needs to generate an elm application for each database,
generate elm source code and compile that elm code with caching. It
uses Starmelon to run derive macros written in Elm.
4. AstridLabs needs to create a heavily modified copy of an existing elm
application with tons of generated code. It uses Starmelon to run
derive macros written in Elm.
For 3 and 4 I could speed up the code generation step by using
part of starmelon as library. A proc-macro could include the Elm derive
macro javascript at crate build time and reuse the same v8 isolate over
and over for every web request.
My plan for 1,2,3,4 has a lot of shared functionality. I am thinking
that I should consolidate all the components into one library crate.
Introduce starmelon, a program for executing elm functions with input
from files and writing the output back to files.
Support evaluating 4 types of values and 12 types of functions.
```elm
x : String
x : Bytes
x : VirtualDom.Node msg
x : Json.Encode.Value
f : String -> String
f : String -> Bytes
f : String -> VirtualDom.Node msg
f : String -> Json.Encode.Value
f : Bytes -> String
f : Bytes -> Bytes
f : Bytes -> VirtualDom.Node msg
f : Bytes -> Json.Encode.Value
f : Json.Encode.Value -> String
f : Json.Encode.Value -> Bytes
f : Json.Encode.Value -> VirtualDom.Node msg
f : Json.Encode.Value -> Json.Encode.Value
```
My target use case for starmelon is generating html files. It is nice
to be able to write parameterized framgents of markup in multiple
modules and then compose them into a final value. I also have in mind
attempting to replace helm (kubernetes pacakge manager) because I hate
how error prone its string based templating language is.
