Ensure Ops.xts results has index and no names

Calling Ops.xts() on a matrix and a xts object without a dim attribute
can result in an xts object without an index, and/or with a names
attribute.

Ensure there is never a names attribute, and that we always check if
the index exists.

Tests only exercise the subtraction operator. There should be tests
that use relational operators.

See #295.

R/Ops.xts.R

@@ -49,7 +49,6 @@ function(e1, e2)
     #.Call('add_xts_class', e)
     .Call('add_class', e, CLASS, PACKAGE="xts")
   }
-  else 
   if(is.null(attr(e,'index'))) {
     if(is.xts(e1)) {
       e <- .xts(e, .index(e1))
@@ -64,5 +63,6 @@ function(e1, e2)
       dimnames(e)[[1]] <- list(NULL)
     }
   }
+  attr(e, "names") <- NULL
   e
 }

inst/unitTests/runit.Ops.R

@@ -98,3 +98,57 @@ test.xts1d_minus_vector_names <- function() {
   colnames(x) <- colnames(y) <- "x"
   checkIdentical(x-M, y)
 }
+
+### xts vector, matrix/vector
+test.xts_vector_minus_matrix1d <- function() {
+  rn <- format(.POSIXct(1:3))
+  cn <- "x"
+  x <- drop(.xts(1:3, 1:3))
+  m <- matrix(1:3, 3, 1, dimnames = list(rn, cn))
+  y <- .xts(1:3*0L, 1:3, dimnames = list(NULL, cn))
+
+  # use checkEquals because attributes change order
+  checkEquals(x-m, y)
+  # test again with no rownames
+  rownames(m) <- NULL
+  checkEquals(x-m, y)
+  # test again with no rownames or colnames
+  colnames(m) <- colnames(y) <- NULL
+  checkEquals(x-m, y)
+  # test again with only colnames
+  colnames(m) <- colnames(y) <- cn
+  checkEquals(x-m, y)
+}
+
+test.xts_vector_minus_matrix2d <- function() {
+  # FIXME:
+  rn <- format(.POSIXct(1:3))
+  cn <- c("x", "y")
+  x <- drop(.xts(1:3, 1:3))
+  m <- matrix(1:6, 3, 2, dimnames = list(rn, cn))
+  y <- .xts(cbind(1:3*0L, 1:3-4:6), 1:3, dimnames = list(NULL, cn))
+
+  # use checkEquals because attributes change order
+  checkEquals(x-m, y)
+  # test again with no rownames
+  rownames(m) <- NULL
+  checkEquals(x-m, y)
+  # test again with no rownames or colnames
+  colnames(m) <- colnames(y) <- NULL
+  checkEquals(x-m, y)
+  # test again with only colnames
+  colnames(m) <- colnames(y) <- cn
+  checkEquals(x-m, y)
+}
+
+test.xts_vector_minus_vector <- function() {
+  # FIXME:
+  m <- 1:3
+  x <- drop(.xts(m, 1:3))
+  y <- drop(.xts(m*0L, 1:3))
+
+  checkIdentical(x-m, y)
+  # add names to vector
+  names(m) <- format(index(x))
+  checkIdentical(x-m, y)
+}