closes #3, #4

NEWS.md

@@ -1,6 +1,13 @@
 
 # dotty 0.2.0  (UNRELEASED)
 
+- Fixed an issue where invocations like `.[a, .., z] <- letters` would
+  also create a binding called `..`. (#4)
+
+- `dotty` now requires all arguments within a `.[]` invocation to be
+  either named or unnamed -- that is, `.[a = a, b] <- c(a = "a", b = "b")`
+  are now disallowed. This may be relaxed in a future release. (#3)
+
 - `dotty::dotify()` is now exported for use by R packages which would
   like to use `dotty` internally. (#1)
 

R/dot.R

@@ -77,7 +77,7 @@ dotty <- function(parts, value, envir) {
   # lhs and rhs parts, and apply on each side
   # split into left parts, right parts
   nlhs <- index - 1L
-  nrhs <- length(parts) - index + 1L
+  nrhs <- length(parts) - index
 
   # evaluate left variables
   dotty_impl(
@@ -99,6 +99,13 @@ dotty <- function(parts, value, envir) {
 
 dotty_impl <- function(parts, value, envir) {
 
+  nms <- names(parts)
+  if (is.character(nms)) {
+    n <- sum(nms == "")
+    if (!n %in% c(0L, length(nms)))
+      stop("cannot mix named with unnamed arguments in `.[]` invocations")
+  }
+
   for (i in seq_along(parts)) {
 
     part <- parts[[i]]

tests/testthat/test-dot.R

@@ -101,3 +101,21 @@ test_that("dotify helps codetools understand dotty usages", {
   expect_true(grepl("cherry", messages))
 
 })
+
+test_that("dotty doesn't create a variable called '..'", {
+
+  .[a, .., z] <- letters
+  expect_equal(a, "a")
+  expect_equal(z, "z")
+  expect_false(exists(".."))
+
+})
+
+test_that("we require all arguments to be named or unnamed", {
+
+  expect_error({
+    data <- list(w = 1, x = 2, y = 3, z = 4)
+    .[apple = x, banana] <- data
+  })
+
+})