elm-tigershark

elm-tigershark

WIP/Exploratory project for generating TypeScript type declarations for Elm programs. Based off of elm-typescript-interop.

Roadmap

• Setup TypeScript and Elm project
• Setup Elm testing
• Use elm-syntax to parse main module source and extract relivent ASTs
• Convert interoperable Elm types into TypeScript types
• Add types for flags
• Add types for all ports in file
• Parse a single module to a declaration file
• CLI tool
• Resolve type aliases
• Include imported ports
• Multi-module parsing
• Good error messages, CLI enhancements
• Support pre-0.19 Elm

Some notes

let's generate a type declaration file!
    |
    v
run `tigershark src/Main.elm --output=src/main.d.ts`
    |                                |
    |                                `----> Fail, malformed CLI args
    v
locate and parse Elm project file    -----> Fail, project file not found
    |                                             unsupported Elm version
    v
collect all project file paths and
source code, pass over to Elm
    |
    v
initialize module cache
    |
    v
parse module with `elm-syntax`       -----> Fail, unable to find module in cache
    |                                             unable to parse module source
    v
collect module name, main function   -----> Fail, no main or no signature
    |
    v
extract flags type AST from main sig -----> Fail, main is not a `Program`
    |
    v
if ports module, search module       -----> Fail, unable to find import in cache
cache and collect port definitions                unable to parse module source
    |
    v
convert flags/ports to Typescript    -----> Fail, type is not interoperable
type strings, resolve local and                   alias type not found
imported aliases                                  unable to find import
    |                                             unable to parse module source
    v
stringify module name, flags, ports
    |
    v
generate declaration file
    |
    v
write output file                    -----> Fail, error writing output

Later enhancements

Things I'm thinking about now, but should be done later.

• Flag to use local prettier install to format declaration files, and optionally specify the location of the prettier executable.
• Flag to try type checking the code first with the elm compiler, and optionally specify the location of the elm make executable.
• Flag for watch mode.
• Flag to set if the declaration file matches on *.elm, or specific modules.
• Write custom "isPortsModule" parser so that we don't have to fully parse every imported module to find ones that use ports.
• Request files as needed from node, instead of reading all files during startup.
• Fuzz tests for
  • Always extracts name from module
  • Always converts flags of interoperable types
  • Always collects local ports
• Use elm-program-test to test the worker program end-to-end.
• And/Or, do full end-to-end testing like elm-typescript-interop by generating and diffing files.
• Windows file path support

The name

This isn't a useful tool yet so it doesn't have a useful tool name. TypeScript and Tigershark sound a bit similar. That's all I've got.