Do not prepend / append with a semicolon the only JSX element in a program

[sapegin]

Don't output semicolon before or after a single [ExpressionStatement whose expression is a JSXElement] inside a markdown code block, regardless of the semi option.

I’m not sure how to check that we’re inside Markdown.

Fixes #3196.

[azz]

I’m not sure how to check that we’re inside Markdown.

One way to do this is expose the parent parser:

multiparser.js:

  next.options = Object.assign({}, options, next.options, {
+   parentParser: options.parser,
    originalText: next.text
  });

Then check with:

if (options.parentParser === "markdown") {
  // ...
}

[sapegin]

@azz Thanks, it seems to work! Please have a look. Is there anything I need to change? This is my first PR to Prettier ;-)

[suchipi]

Looks good to me 👍