Fix exception in textMatchScore() when text is empty

[mickael-menu]

I observed an exception thrown from textMatchScore() if text is empty, because matches[0].errors is undefined in this case:

client/src/annotator/anchoring/match-quote.js

Line 63 in da3a346

return 1 - (matches[0].errors / str.length);

An empty text occurs when the length of the context.prefix is larger than the prefix of the first match in the page. It gives a negative first parameter for this slice():

client/src/annotator/anchoring/match-quote.js

Line 119 in da3a346

text.slice(match.start - context.prefix.length, match.start),

[codecov]

Codecov Report

Merging #3538 (b0d0165) into master (da3a346) will not change coverage.
The diff coverage is n/a.

❗ Current head b0d0165 differs from pull request most recent head 895dd5e. Consider uploading reports for the commit 895dd5e to get more accurate results

@@           Coverage Diff           @@
##           master    #3538   +/-   ##
=======================================
  Coverage   98.60%   98.60%           
=======================================
  Files         211      211           
  Lines        7697     7697           
  Branches     1750     1750           
=======================================
  Hits         7590     7590           
  Misses        107      107           

Impacted Files	Coverage Δ
src/annotator/anchoring/match-quote.js	100.00% <ø> (ø)

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[robertknight]

Hello,

Thanks for the PR. Would you mind adding a unit test for matchQuote that reproduces the original issue (when context.prefix.length exceeds text.length).

[mickael-menu]

@robertknight Sure, here's the test run from master:

SUMMARY:
✔ 2833 tests completed
✖ 1 test failed

FAILED TESTS:
  matchQuote
    ✖ matches with a context prefix longer than the text
      Chrome Headless 92.0.4512.0 (Mac OS 10.15.7)
    TypeError: Cannot read property 'errors' of undefined
        at textMatchScore (/var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/annotator/anchoring/match-quote.js:63:26 <- /var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/b2022ad174868b7c5ac8d9da8c2e4ae8.browserify.js:165247:25)
        at scoreMatch (/var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/annotator/anchoring/match-quote.js:118:9 <- /var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/b2022ad174868b7c5ac8d9da8c2e4ae8.browserify.js:165319:96)
        at /var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/annotator/anchoring/match-quote.js:152:12 <- /var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/b2022ad174868b7c5ac8d9da8c2e4ae8.browserify.js:165348:14
        at Array.map (<anonymous>)
        at matchQuote (/var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/annotator/anchoring/match-quote.js:149:33 <- /var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/b2022ad174868b7c5ac8d9da8c2e4ae8.browserify.js:165342:59)
        at Context.<anonymous> (/var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/annotator/anchoring/test/match-quote-test.js:200:19 <- /var/folders/ks/ny2nfkh5183ffwm10fw_9rq80000gn/T/b2022ad174868b7c5ac8d9da8c2e4ae8.browserify.js:171460:46)

TOTAL: 1 FAILED, 2833 SUCCESS

[robertknight]

Looks good to me. I made a couple of additional changes on this branch:

• I revised the description of the prefix test to better describe the condition when text.slice(...) was producing an empty output before
• I added an additional test case that covers a related issue that could happen when generating a score for the suffix match. The existing changes in textMatchScore already fixed the problem.

[robertknight]

These changes have been shipped in client version v1.809.0.

[mickael-menu]

Sounds good, thanks for reviewing my PR 👍