v0.12.3

• Ensure JSX element names start with a capital letter (#1309)

  The JSX specification only describes the syntax and says nothing about how to interpret it. But React (and therefore esbuild) treats JSX tags that start with a lower-case ASCII character as strings instead of identifiers. That way the tag <i/> always refers to the italic HTML element i and never to a local variable named i.

  However, esbuild may rename identifiers for any number of reasons such as when minification is enabled. Previously esbuild could sometimes rename identifiers used as tag names such that they start with a lower-case ASCII character. This is problematic when JSX syntax preservation is enabled since subsequent JSX processing would then turn these identifier references into strings.

  With this release, esbuild will now make sure identifiers used in tag names start with an upper-case ASCII character instead when JSX syntax preservation is enabled. This should avoid problems when using esbuild with JSX transformation tools.

• Fix a single hyphen being treated as a CSS name (#1310)

  CSS identifiers are allowed to start with a - character if (approximately) the following character is a letter, an escape sequence, a non-ASCII character, the character _, or another - character. This check is used in certain places when printing CSS to determine whether a token is a valid identifier and can be printed as such or whether it's an invalid identifier and needs to be quoted as a string. One such place is in attribute selectors such as [a*=b].

  However, esbuild had a bug where a single - character was incorrectly treated as a valid identifier in this case. This is because the end of string became U+FFFD (the Unicode replacement character) which is a non-ASCII character and a valid name-start code point. With this release a single - character is no longer treated as a valid identifier. This fix was contributed by @lbwa.