VS Code snippet transform: convert camel case to Pascal case or vice versa

gistfile1.txt

// If you want to convert a PascalCase variable to camelCase, you can do the following:
// Where `n` is the tab stop you want to reference
${n/^(.)(.*)$/${1:/downcase}${2}/}

// Example: ${1:This is my original} => ${1/^(.)(.*)$/${1:/downcase}${2}/}


// If you want to convert a camelCase variable to PascalCase, you can do the following:
// Where `n` is the tab stop you want to reference
${n/^(.)(.*)$/${1:/upcase}${2}/}

// Example: ${1:This is my original} => ${1/^(.)(.*)$/${1:/upcase}${2}/}

My only issue was forgetting to hit tab while designing the snippet as the transform is not applied until you attempt to navigate to the next tabstop. Thank you for this regex and options combination as it is a very common and useful one.

Seems like there is /camelcase and /pascalcase transform, which could make everything simpler.
But this acts like it's meant to convert snake_case to camelCase, not PascalCase to camelCase.
There is also /capitalize transform, which can be used for converting camelCase to PascalCase, but there is no opposite transform.

Therefore these do give expected result,

${1:snake_to_camel} => ${1/(.*)/${1:/camelcase}/} // result is "snakeToCamel"
${2:snake_to_pascal} => ${2/(.*)/${1:/pascalcase}/} // result is "SnakeToPascal"
${3:camelToPascal} => ${3/(.*)/${1:/capitalize}/} // result is "CamelToPascal"

But these do not give expected result.

${1:PascalToCamel} => ${1/(.*)/${1:/camelcase}/} // result is "pascaltocamel"
${2:camelToPascal} => ${2/(.*)/${1:/pascalcase}/} // result is "Cameltopascal"

What a mess.

thank you

Answer to vscode snippet transform file name in the snippet to camel case or pascal case variable

given file_name_foo.ext file

${TM_FILENAME_BASE/^(.*)_foo$/${1:/pascalcase}/}  ==> FileName
${TM_FILENAME_BASE/^(.*)_foo$/${1}/}  ==> file_name
${TM_FILENAME_BASE/^(.*)_foo$/${1:/upcase}/}  ==> FILE_NAME

:/camelcase works as well.