Snapshot got 'Formatter buffer never received a formatted value' in v0.20

[zaaack]

It would fail in second time(compare). First time it success and output a snap file and a md file.

But this is totally OK in v0.18

  1 passed
  1 failed

  Root render
  /Users/z/Projects/Douban/share/helpcenter/helpcenter/static-source/feedback-popup/node_modules/concordance/lib/formatUtils.js:113

  Rejected promise returned by test. Reason:

  Error {
    message: 'Formatter buffer never received a formatted value.',
  }

  SingleValueFormatter.finalize (node_modules/concordance/lib/formatUtils.js:113:31)
  Object.diffDescriptors (node_modules/concordance/lib/diff.js:379:27)
  _callee$ (test/root.test.js:41:11)
  tryCatch (node_modules/regenerator-runtime/runtime.js:65:40)
  Generator.invoke [as _invoke] (node_modules/regenerator-runtime/runtime.js:303:22)
  Generator.prototype.(anonymous function) [as next] (node_modules/regenerator-runtime/runtime.js:117:21)
  Test.fn (test/root.test.js:39:1)

root.test.js.md

# Snapshot report for `test/root.test.js`

The actual snapshot is saved in `root.test.js.snap`.

Generated by [AVA](https://ava.li).

## Root render

> Snapshot 1

    <div
      className="feedback-ulwj3d7qthha"
      onClick={Function bound hideDialogOnOverlay {}}
    >
      <div
        className="dialog-container"
      >
        <form
          className="dialog"
          onSubmit={Function bound submit {}}
        >
          <div
            className="close"
            onClick={Function bound hideDialog {}}
          >
            ×
          </div>
          <div
            className="title"
          >
            请填写反馈内容
          </div>
          <div
            className="editor"
          >
            <textarea
              maxLength={1000}
              name="feedback"
              onChange={Function bound handleChange {}}
              placeholder="请填写"
              value=""
            />
        
          </div>
          <div
            className="title"
          >
            上传图片
          </div>
          <div
            className="captures"
          >
            <span
              className="rc-upload pic add"
              onClick={Function {}}
              onDragOver={Function {}}
              onDrop={Function {}}
              onKeyDown={Function {}}
              role="button"
              style={undefined}
              tabIndex="0"
            >
              <input
                accept="image/*,.txt,.doc,.docx"
                multiple={true}
                onChange={Function {}}
                style={
                  {
                    display: 'none',
                  }
                }
                type="file"
              />
              <div
                className="h-line"
              />
              <div
                className="v-line"
              />
            </span>
          </div>
          <div
            className="tips"
          >
            可以上传不超过3个文件，每个限制最大为1MB，类型限制为 jpg / jpeg / gif / png / txt / docx / doc
          </div>
          <div
            className="btn-submit"
            onClick={Function bound submit {}}
          >
            好了，发送反馈
          </div>
        </form>
      </div>
    </div>

root.test.js.snap
root.test.js.snap.zip

[novemberborn]

@zaaack would you able to share the test itself? Or perhaps find a reproducible test case?

Snapshot assertions shouldn't fail without changes, so that's definitely odd. However the crash occurs when rendering the diff, so we don't know what the change was!

I know what's going wrong, but I can't think of a situation where that would occur. So if you could share failing code that would be much appreciated.

[zaaack]

@novemberborn I think I find out why, it's caused by an undefined property changed to not undefined, or the opposite.

Here is a minimal reproduce project: https://github.com/zaaack/ava-issue-1433/blob/master/src/Feedback.js#L38

[novemberborn]

@zaaack thanks for the reproduction. I've got a fix in concordancejs/concordance#35. If you could install that version next to AVA it should get picked up. I'll try and get a release out soon.