Actually, since the question was posed a few new built-in variables have been added,
including TM_FILENAME_BASE
. See snippet variables documentation. So there is no need to do a transform just to get the filename without the extension.
Here is the current list of snippet variables:
TM_SELECTED_TEXT The currently selected text or the empty string
TM_CURRENT_LINE The contents of the current line
TM_CURRENT_WORD The contents of the word under cursor or the empty string
TM_LINE_INDEX The zero-index based line number
TM_LINE_NUMBER The one-index based line number
TM_FILENAME The filename of the current document
TM_FILENAME_BASE The filename of the current document without its extensions
TM_DIRECTORY The directory of the current document
TM_FILEPATH The full file path of the current document
CLIPBOARD The contents of your clipboard
WORKSPACE_NAME The name of the opened workspace or folder
CURRENT_YEAR The current year
CURRENT_YEAR_SHORT The current year's last two digits
CURRENT_MONTH The month as two digits (example '02')
CURRENT_MONTH_NAME The full name of the month (example 'July')
CURRENT_MONTH_NAME_SHORT The short name of the month (example 'Jul')
CURRENT_DATE The day of the month
CURRENT_DAY_NAME The name of day (example 'Monday')
CURRENT_DAY_NAME_SHORT The short name of the day (example 'Mon')
CURRENT_HOUR The current hour in 24-hour clock format
CURRENT_MINUTE The current minute
CURRENT_SECOND The current second
CURRENT_SECONDS_UNIX The number of seconds since the Unix epoch
For inserting line or block comments, honoring the current language:
BLOCK_COMMENT_START Example output: in PHP /* or in HTML <!--
BLOCK_COMMENT_END Example output: in PHP */ or in HTML -->
LINE_COMMENT Example output: in PHP // or in HTML <!-- -->
vscode v1.66 will add two new variables:
CURSOR_INDEX 0-based
CURSOR_NUMBER 1-based
The above two work with multiple cursors so that each cursor position (same as a selection) will have an incremented integer inserted.
For an example of this, see https://stackoverflow.com/a/69946559/836330
It looks like v1.40 will add:
WORKSPACE_FOLDER Path of workspace directory
RANDOM Insert 6 random digits
RANDOM_HEX Insert 6 random hex digits
See https://github.com/microsoft/vscode/pull/82529 and https://github.com/microsoft/vscode/pull/79764
v1.53 will add the relative path from the root folder to the current file:
RELATIVE_FILEPATH
UUID
See https://github.com/microsoft/vscode/pull/114208 and https://github.com/microsoft/vscode-docs/blob/vnext/release-notes/v1_53.md#new-snippet-variables