explicit_return_linter XPath

explicit_return_linter.R

  allowed_functions <- c(
    # Normal calls
    "return", "stop", "warning", "message", "stopifnot", "q", "quit",
    "invokeRestart", "tryInvokeRestart",

    # Normal calls from non-default libraries
    "LOG", "abort",

    # tests in the RUnit framework are functions ending with a call to one
    #   of the below. would rather users just use a different framework
    #   (e.g. testthat or tinytest), but already 250+ BUILD files depend
    #   on RUnit, so just cater to that. confirmed the efficiency impact
    #   of including these is minimal.
    # RUnit tests look like 'TestInCamelCase <- function()'
    #   NB: check for starts-with(text(), 'Test') below is not sufficient, e.g.
    #   in cases of a "driver" test function taking arguments and the main unit
    #   test iterating over those.
    "checkEquals", "checkEqualsNumeric", "checkException", "checkIdentical",
    "checkStop", "checkTrue", "checkWarnings",

    # Functions related to S3 methods
    "UseMethod", "NextMethod",

    # Functions related to S4 methods
    "standardGeneric", "callNextMethod",

    # Functions related to C interfaces
    ".C", ".Call", ".External", ".Fortran"
  )

  preceding_control_calls <-
    .Paste0or("preceding-sibling::", c("IF", "FOR", "WHILE", "REPEAT"))

  # from top, look for a FUNCTION definition that uses { (one-line
  #   function definitions are excepted), then look for failure to find
  #   return() on the last() expr of the function definition.
  # exempt .onLoad which shows up in the tree like
  #   <expr><expr><SYMBOL>.onLoad</></><LEFT_ASSIGN></><expr><FUNCTION>...
  # simple final expression (no control flow) must be
  # <expr><expr> CALL( <expr> ) </expr></expr>
  # NB: if this syntax _isn't_ used, the node may not be <expr>, hence
  #   the use of /*[...] below and self::expr here. position() = 1 is
  #   needed to guard against a few other cases.
  #   We also need to make sure that this expression isn't followed by a pipe
  #   symbol, which would indicate that we need to also check the last
  #   expression.
  # pipe expressions are like
  #   ...
  #   <SPECIAL>%&gt;%</SPECIAL>
  #   <expr><expr><SYMBOL_FUNCTION_CALL>return</SYMBOL_FUNCTION_CALL>
  #   </expr></expr>
  # Unlike the following case, the return should be the last expression in
  # the sequence.
  # conditional expressions are like
  #   <expr><IF> ( <expr> ) <expr> [ <ELSE> <expr>] </expr>
  # we require _any_ call to return() in either of the latter two <expr>, i.e.,
  #   we don't apply recursive logic to check every branch, only that the
  #   two top level branches have at least two return()s
  # because of special 'in' syntax for 'for' loops, the condition is
  #   tagged differently than for 'if'/'while' conditions (simple PAREN)
  xpath <- glue("
  //FUNCTION[parent::expr[not(
    preceding-sibling::expr[SYMBOL[{ .XpTextInTable(.kReturnNotNeededFuns) }]]
    or (
      preceding-sibling::expr/SYMBOL[starts-with(text(), 'Test')]
      and not(SYMBOL_FORMALS)
    )
  )]]
    /following-sibling::expr[OP-LEFT-BRACE and expr[last()]/@line1 != @line1]
    /expr[last()]
    /*[
      (
        ({ preceding_control_calls })
        and (preceding-sibling::OP-RIGHT-PAREN or preceding-sibling::forcond)
        and self::expr[not(
          .//SYMBOL_FUNCTION_CALL[{ .XpTextInTable(allowed_functions) }]
        )]
      ) or (
        not({ preceding_control_calls })
        and not(self::IF or self::FOR or self::WHILE or self::REPEAT)
        and (
          (
            position() = last()
            and (
              preceding-sibling::PIPE
              or preceding-sibling::SPECIAL[text() = '%>%']
            )
            and not(self::expr/expr/SYMBOL_FUNCTION_CALL[
              { .XpTextInTable(allowed_functions) }
            ])
          ) or (
            position() = 1
            and not(
              following-sibling::PIPE
              or following-sibling::SPECIAL[text() = '%>%']
            )
            and not(self::expr/SYMBOL_FUNCTION_CALL[
              { .XpTextInTable(allowed_functions) }
            ])
          )
        )
      )
    ]
  ")