split code into more tokens to fix sourcemap-validator warnings

[connorjclark]

Fixes https://github.com/webpack/webpack/issues/8302

Add more nodes to create a more granular identity source map. This allows for better source maps when other consumers process what webpack creates (I've been using the terser plugin).

Previous splitting resulted in this (this is post-terser):

note that all mappings map to column 0 for every line.

Now:

I also added a test that did a (too simple) check w/ sourcemap-validator. It passes even w/o these changes - I didn't spend any time thinking about how to create a test case that would mimic what terser was doing. Perhaps someone could help with that?

[jsf-clabot]

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[codecov[bot]]

Codecov Report

Merging #51 into master will decrease coverage by 61.66%. The diff coverage is 100%.

@@             Coverage Diff             @@
##           master      #51       +/-   ##
===========================================
- Coverage   78.25%   16.58%   -61.67%     
===========================================
  Files          11        8        -3     
  Lines         492      416       -76     
  Branches       76       67        -9     
===========================================
- Hits          385       69      -316     
- Misses        107      347      +240

Impacted Files	Coverage Δ
lib/OriginalSource.js	89.47% <100%> (-10.53%)	:arrow_down:
lib/ReplaceSource.js	3.6% <0%> (-92.79%)	:arrow_down:
lib/ConcatSource.js	9.09% <0%> (-80%)	:arrow_down:
lib/PrefixSource.js	15% <0%> (-67.5%)	:arrow_down:
lib/RawSource.js	23.52% <0%> (-64.71%)	:arrow_down:
lib/CachedSource.js	4.87% <0%> (-41.47%)	:arrow_down:
lib/SourceAndMapMixin.js	66.66% <0%> (-33.34%)	:arrow_down:
lib/Source.js	15.78% <0%> (-15.79%)	:arrow_down:
lib/SourceMapSource.js
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update b9529e9...9aab3a7. Read the comment docs.

[codecov[bot]]

Codecov Report

Merging #51 into master will decrease coverage by 61.66%. The diff coverage is 100%.

@@             Coverage Diff             @@
##           master      #51       +/-   ##
===========================================
- Coverage   78.25%   16.58%   -61.67%     
===========================================
  Files          11        8        -3     
  Lines         492      416       -76     
  Branches       76       67        -9     
===========================================
- Hits          385       69      -316     
- Misses        107      347      +240

Impacted Files	Coverage Δ
lib/OriginalSource.js	89.47% <100%> (-10.53%)	:arrow_down:
lib/ReplaceSource.js	3.6% <0%> (-92.79%)	:arrow_down:
lib/ConcatSource.js	9.09% <0%> (-80%)	:arrow_down:
lib/PrefixSource.js	15% <0%> (-67.5%)	:arrow_down:
lib/RawSource.js	23.52% <0%> (-64.71%)	:arrow_down:
lib/CachedSource.js	4.87% <0%> (-41.47%)	:arrow_down:
lib/SourceAndMapMixin.js	66.66% <0%> (-33.34%)	:arrow_down:
lib/Source.js	15.78% <0%> (-15.79%)	:arrow_down:
lib/SourceMapSource.js
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update b9529e9...1b0d706. Read the comment docs.