Add ES5 check to syntax test

[rreusser]

See #1539. Uses another eslint pass that applies no rules except for an ecmaVersion: 5 parser setting. Before the const fix, this change causes plotly-latest to return:

$ npm run test-syntax

/Users/rreusser/plotly/plotly.js/dist/plotly-gl2d.js
  435:1  error  Parsing error: The keyword 'const' is reserved

/Users/rreusser/plotly/plotly.js/dist/plotly-gl3d.js
  1105:1  error  Parsing error: The keyword 'const' is reserved

/Users/rreusser/plotly/plotly.js/dist/plotly-with-meta.js
  1916:1  error  Parsing error: The keyword 'const' is reserved

/Users/rreusser/plotly/plotly.js/dist/plotly.js
  1916:1  error  Parsing error: The keyword 'const' is reserved

✖ 4 problems (4 errors, 0 warnings)

test-syntax error [es5-only syntax]

ok no jasmine suites focus/exclude blocks
ok circular dependencies: 17
ok correct headers and contents in lib/ and src/
ok lower case only file names
ok trailing new line character
/Users/rreusser/plotly/plotly.js/tasks/test_syntax.js:250
        throw new Error('test syntax failed.');
        ^

Error: test syntax failed.
    at process.<anonymous> (/Users/rreusser/plotly/plotly.js/tasks/test_syntax.js:250:15)
    at emitOne (events.js:96:13)
    at process.emit (events.js:188:7)

After fixing:

$ npm run test-syntax

ok es5-only syntax
ok no jasmine suites focus/exclude blocks
ok circular dependencies: 17
ok correct headers and contents in lib/ and src/
ok lower case only file names
ok trailing new line character

[rreusser]

Note: CI failure can be considered a success. 🎉

[rreusser]

I've negated a negation… that's silly.

[etpinard]

Why not just use this list, something like:

var validFiles = constants.partialBundlePaths(function(p) { return p.dist; });
validFiles  = validFiles.concat(constants.pathToPlotlyDist)l

var report = cli.executeOnFiles(validFiles);
// ...

looks easier to read to me. Thoughts?

[rreusser]

Sounds great. Didn't know it was a thing. Will update once confirmed it works.

[rreusser]

Fixed. Included plotly.js but left out with with-meta to save a few seconds.

[etpinard]

Too bad eslint can't do this in an async way. This does slow down test-syntax a lot. Oh well, it's worth it 👍

[rreusser]

There's always the possibility of just testing the regular bundle only since there's tons of duplication between the bundles, but I'd need to investigate to figure out which parts are a subset of which parts.

[rreusser]

Fixed file lookup. FYI you can just switch ecmaVersion between 5 an 6 to test success/failure.

[etpinard]

💃 after merging master ✅