cwltool --validate should validate that javascript expressions are valid ES5 expressions

[ThomasHickman]

It would be nice if cwltool --validate would report ES5 syntax errors in cwl expressions e.g. running cwltool --validate with this:

cwlVersion: v1.0
requirements:
- class: InlineJavascriptRequirement
inputs:
  - id: parameter
    type: string
    inputBinding:
      valueFrom: $((_ => "test")())
outputs: []
class: CommandLineTool
baseCommand: echo

would report an error, as it uses ES6 syntax.

[tetron]

That's a good idea, it would probably require a small parser that checks for valid ES5 grammar.

[ThomasHickman]

If depending on node and npm is acceptable, you could use eslint - which by default parses as ES5 (https://eslint.org/docs/user-guide/configuring#specifying-parser-options)

[ThomasHickman]

I'm working on this at the moment

[tetron]

From gitter:

I think the gist is you want to call schema.get_metaschema() which returns a loader, use the loader object to load the CWL schema, iterate over the loaded CWL schema to find each field and then finally search the field for the Expression type.

Using eslint seems like a fine solution, but I'm not sure how best to manage the dependency. If Docker is availabe we use node:slim image, that could be switched to a custom image which also had eslint installed. If using a locally installed node, either we install eslint automatically (uhg?) or make it the user's problem. Probably this needs to be an optional dependency.

[ThomasHickman]

@tetron - I think using jshint might actually be a better solution - it shows better errors when users use ES6 features when the parsing mode is ES5.

RE managing the dependancy: we could on installation of cwltool, pull jshint/eslint from a CDN which serves a one file javascript containing jshint (so we can get jshint without node/npm) - then if a user runs cwltool without node installed and a InlineJavascriptRequirement requirement cwltool should print a warning. This avoids giving the user responsibility of installing jshint/eslint, making a dependancy on docker or making the full installation have a dependancy on npm/node

[tetron]

If eslint or jshint can be easily packed into one file, and the licensing is compatible, it would be even better to add it to the cwltool repo so it can be packaged and distributed as part of cwltool, and read in as a package resource on the fly.

[ThomasHickman]

Yes, I think that would be better, and both eslint and jshint have MIT licenses