Refactor minify-numeric-literals.

[bardiharborow]

I went ahead and rewrote the test suite for minify-numeric-literals, and came across a number of issues:

• 0xa should transform to 10, instead of 0xa
• 0x64 should transform to 100 instead of 1e2 (opinionated, better gzip?)
• 0o12 should transform to 10 instead of 1e1
• 0o144 should transform to 100 instead of 1e2 (opinionated, better gzip?)
• 0b1010 should transform to 10 instead of 1e1
• 0b1100100 should transform to 100 instead of 1e2 (opinionated, better gzip?)
• 0.123456 should transform to .123456 instead of 0.123456
• 1.5e3 should transform to 1500 instead of 1.5e3
• 1e-1 should transform to .1 instead of 1e-1
• 1e-2 should transform to .01 instead of 1e-2
• 1e-3 should transform to .001 instead of 1e-3 (opinionated, better gzip?)
• 1.5e-3 should transform to .0015 instead of 1.5e-3

I investigated several different ways of writing logic to solve this, but the simplest way I can find is to compare the length of .toString() and .toExponential() and to choose the shortest. Additionally I've removed the .replaceWith in favor of editing path.node.extra.raw in-place. This prevents the NumericLiteral from being re-entered immediately, but I'm unsure if this is good practice or not.

This PR has now been rewritten a little and incorporates the optimisations from #467.

Closes #467 and fixes #459.

[kangax]

Don't the last 5 cases already work this way? I can see it in a REPL. As far as leading 0, isn't this something that's controlled by Babel printer?

[bardiharborow]

@kangax you are correct, but it's not minify-numeric-literals that's doing that, it's constant-folding. If I run my refactored tests without the associated plugin fixes, I get this:

Summary of all failing tests
 FAIL  packages/babel-plugin-minify-numeric-literals/__tests__/numeric-literals-test.js
  ● numeric-literals › should shorten hexadecimal literals correctly

    expect(received).toBe(expected)
    
    Expected value to be (using ===):
      "[1, 10, 100, 1e3, 0xfffffff, -1, -10, -100, -1e3, -0xfffffff];"
    Received:
      "[1, 0xa, 1e2, 1e3, 0xfffffff, -1, -0xa, -1e2, -1e3, -0xfffffff];"
      
      at Object.<anonymous> (packages/babel-plugin-minify-numeric-literals/__tests__/numeric-literals-test.js:24:31)

  ● numeric-literals › should shorten octal literals correctly

    expect(received).toBe(expected)
    
    Expected value to be (using ===):
      "[1, 10, 100, 1e3, -1, -10, -100, -1e3];"
    Received:
      "[1, 1e1, 1e2, 1e3, -1, -1e1, -1e2, -1e3];"
      
      at Object.<anonymous> (packages/babel-plugin-minify-numeric-literals/__tests__/numeric-literals-test.js:31:31)

  ● numeric-literals › should shorten binary literals correctly

    expect(received).toBe(expected)
    
    Expected value to be (using ===):
      "[1, 10, 100, 1e3, -1, -10, -100, -1e3];"
    Received:
      "[1, 1e1, 1e2, 1e3, -1, -1e1, -1e2, -1e3];"
      
      at Object.<anonymous> (packages/babel-plugin-minify-numeric-literals/__tests__/numeric-literals-test.js:38:31)

  ● numeric-literals › should shorten floats correctly

    expect(received).toBe(expected)
    
    Expected value to be (using ===):
      "[.123456, 1.23456, 12.3456, -.123456, -1.23456, -12.3456];"
    Received:
      "[.123456, 1.23456, 12.3456, -0.123456, -1.23456, -12.3456];"
      
      at Object.<anonymous> (packages/babel-plugin-minify-numeric-literals/__tests__/numeric-literals-test.js:45:31)

  ● numeric-literals › should shorten existing exponential literals correctly

    expect(received).toBe(expected)
    
    Expected value to be (using ===):
      "[10, 1e2, 1500, -10, -1e2, -1500, .1, .01, .0015];"
    Received:
      "[1e1, 1e2, 1.5e3, -1e1, -1e2, -1.5e3, 1e-1, 1e-2, 1.5e-3];"
      
      at Object.<anonymous> (packages/babel-plugin-minify-numeric-literals/__tests__/numeric-literals-test.js:61:31)


Test Suites: 1 failed, 26 passed, 27 total
Tests:       5 failed, 5 skipped, 430 passed, 440 total
Snapshots:   10 passed, 10 total
Time:        19.927s
Ran all test suites.
npm ERR! Test failed.  See above for more details.

As for the leading zero, I'm unfamiliar with how the Babel printer works, but it seems to just echo what ever we give it in path.node.extra.raw.

[kangax]

I can't reproduce this (except for 0. removal).

> require('babel-core').transform('f(1e-1)', {presets:['babili']}).code
'f(0.1);'
> require('babel-core').transform('f(0xa)', {presets:['babili']}).code
'f(10);'
> require('babel-core').transform('f(0x64)', {presets:['babili']}).code
'f(100);'

[bardiharborow]

Ah. The minified: true setting in the preset activates babel-generator/src/generators/types.js#L129, which already implements some of the behaviour I'm adding in my PR. I'd still recommend merging this, as it fixes behavior like changing [1000, 10000] to [1e3, 1e4], but it looks like you may be able to tweak babel-generator and drop minify-numeric-literals completely.

[boopathi]

Can you rebase your branch? Looks like the CI didn't run.

[vigneshshanmugam]

I am not sure why I have used parseFloat instead of this, remember there was a missed optimisation.

[vigneshshanmugam]

@bardiharborow Thanks a lot :)

[bardiharborow]

@vigneshshanmugam Thanks for your extra optimisations too. :)
@boopathi CI is passing now.