enhance tojson()

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: xfun
 Type: Package
 Title: Supporting Functions for Packages Maintained by 'Yihui Xie'
-Version: 0.50.1
+Version: 0.50.2
 Authors@R: c(
   person("Yihui", "Xie", role = c("aut", "cre", "cph"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666", URL = "https://yihui.org")),
   person("Wush", "Wu", role = "ctb"),

NEWS.md

@@ -1,5 +1,7 @@
 # CHANGES IN xfun VERSION 0.51
 
+- `tojson()` supports more types of data now, and will indent sub-elements for lists. See the help page [`?xfun::tojson`](https://git.yihui.org/xfun/manual.html#sec:man-tojson) for details.
+
 # CHANGES IN xfun VERSION 0.50
 
 - The function `isFALSE()` has been removed from this package. The deprecation notice was given two years ago: https://yihui.org/en/2023/02/xfun-isfalse/

R/json.R

@@ -1,49 +1,80 @@
 #' A simple JSON serializer
 #'
 #' A JSON serializer that only works on a limited types of R data (`NULL`,
-#' lists, logical scalars, character/numeric vectors). A character string of the
-#' class `JS_EVAL` is treated as raw JavaScript, so will not be quoted. The
-#' function `json_vector()` converts an atomic R vector to JSON.
+#' lists, arrays, logical/character/numeric vectors). Other types of data will
+#' be coerced to character. A character string of the class `JS_LITERAL` is
+#' treated as raw JavaScript, so will not be quoted. The function
+#' `json_vector()` converts an atomic R vector to JSON.
+#'
+#' Both `NULL` and `NA` are converted to `null`. Named lists are converted to
+#' objects of the form `{key1: value1, key2: value2, ...}`. Unnamed lists are
+#' converted to arrays of the form `[[value1], [value2], ...]`. The same rules
+#' apply to data frames since technically they are also lists. However, please
+#' note that unnamed data frames (i.e., without column names) will be converted
+#' to an array with each _row_ as an array element, whereas named data frames
+#' will have each _column_ as an individual element. For matrices, the JSON
+#' array will have each row as an individual element, and names are discarded.
 #' @param x An R object.
 #' @export
 #' @return A character string.
 #' @seealso The \pkg{jsonlite} package provides a full JSON serializer.
 #' @examples library(xfun)
 #' tojson(NULL); tojson(1:10); tojson(TRUE); tojson(FALSE)
-#' cat(tojson(list(a = 1, b = list(c = 1:3, d = 'abc'))))
-#' cat(tojson(list(c('a', 'b'), 1:5, TRUE)))
+#' tojson(list(a = 1, b = list(c = 1:3, d = 'abc')))
+#' tojson(list(c('a', 'b'), 1:5, TRUE))
+#' tojson(head(iris))  # each column is in an element
+#' tojson(unname(head(iris)))  # each row is in an element
+#' tojson(matrix(1:12, 3))
 #'
-#' # the class JS_EVAL is originally from htmlwidgets::JS()
-#' JS = function(x) structure(x, class = 'JS_EVAL')
-#' cat(tojson(list(a = 1:5, b = JS('function() {return true;}'))))
-tojson = function(x) {
-  if (is.null(x)) return('null')
-  if (is.logical(x)) {
-    if (length(x) != 1 || any(is.na(x)))
-      stop('Logical values of length > 1 and NA are not supported')
-    return(tolower(as.character(x)))
-  }
-  if (is.character(x) && inherits(x, 'JS_EVAL')) return(paste(x, collapse = '\n'))
-  if (is.character(x) || is.numeric(x)) {
-    return(json_vector(x, length(x) != 1 || inherits(x, 'AsIs'), is.character(x)))
+#' # literal JS code
+#' JS = function(x) structure(x, class = 'JS_LITERAL')
+#' tojson(list(a = 1:5, b = JS('function() {return true;}')))
+tojson = function(x) raw_string(.tojson(x), lang = '.json')
+
+.tojson = function(x, n = 1) {
+  make_array = function(..., braces = c('[', ']')) {
+    inner = paste0(strrep('  ', n), ..., collapse = ',\n')
+    paste0(braces[1], '\n', inner, '\n', strrep('  ', n - 1), braces[2])
   }
-  if (is.list(x)) {
+  if (is.null(x)) 'null' else if (is.array(x)) {
+    make_array(apply(x, 1, .tojson, n + 1))
+  } else if (is.list(x)) {
     if (length(x) == 0) return('{}')
-    return(if (is.null(names(x))) {
-      json_vector(unlist(lapply(x, tojson)), TRUE, quote = FALSE)
+    # output unnamed data frames by rows instead of columns
+    nms = names(x)
+    by_row = is.data.frame(x) && is.null(nms)
+    cols = unlist(lapply(x, function(z) {
+      if (by_row) json_atomic(z, FALSE) else .tojson(z, n + 1)
+    }))
+    if (is.null(nms)) {
+      if (by_row) {
+        dim(cols) = dim(x)
+        cols = apply(cols, 1, json_vector, TRUE, FALSE)
+      }
+      make_array(cols)
     } else {
-      nms = quote_string(names(x))
-      paste0('{\n', paste(nms, unlist(lapply(x, tojson)), sep = ': ', collapse = ',\n'), '\n}')
-    })
-  }
-  stop('The class of x is not supported: ', paste(class(x), collapse = ', '))
+      make_array(quote_string(nms), ': ', cols, braces = c('{', '}'))
+    }
+  } else if (is.character(x) && inherits(x, c('JS_LITERAL', 'JS_EVAL'))) {
+    paste(x, collapse = '\n')
+  } else json_atomic(x)
+}
+
+json_atomic = function(x, to_array = NA) {
+    use_quote = !(is.numeric(x) || is.logical(x))
+    asis = inherits(x, 'AsIs')
+    if (is.factor(x)) x = as.character(x)
+    if (is.logical(x)) x = tolower(as.character(x))
+    if (is.na(to_array)) to_array = length(x) != 1 || asis
+    json_vector(x, to_array, use_quote)
 }
 
 #' @param to_array Whether to convert a vector to a JSON array (use `[]`).
 #' @param quote Whether to double quote the elements.
 #' @rdname tojson
 #' @export
 json_vector = function(x, to_array = FALSE, quote = TRUE) {
+  i = is.na(x)
   if (quote) {
     x = quote_string(x)
     x = gsub('\n', '\\\\n', x)
@@ -52,6 +83,7 @@ json_vector = function(x, to_array = FALSE, quote = TRUE) {
     x = gsub('\r', '\\\\r', x)
     x = gsub('\t', '\\\\t', x)
   }
+  x[i] = 'null'
   if (to_array) paste0('[', paste(x, collapse = ', '), ']') else x
 }
 

tests/test-cran/test-json.R

@@ -1,27 +1,26 @@
 library(testit)
 
 assert("tojson() works", {
-  (tojson(NULL) %==% "null")
-  (tojson(list()) %==% "{}")
-  (has_error(tojson(Sys.Date())))
-  (has_error(tojson(NA)))
-  (tojson(NA_character_) %==% '"NA"')
-  (tojson(1:10) %==% "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]")
-  (tojson(TRUE) %==% "true")
-  (tojson(FALSE) %==% "false")
+  (.tojson(NULL) %==% "null")
+  (.tojson(list()) %==% "{}")
+  (.tojson(NA) %==% 'null')
+  (.tojson(NA_character_) %==% 'null')
+  (.tojson(1:10) %==% "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]")
+  (.tojson(TRUE) %==% "true")
+  (.tojson(FALSE) %==% "false")
 
   x = list(a = 1, b = list(c = 1:3, d = "abc"))
-  out = '{\n"a": 1,\n"b": {\n"c": [1, 2, 3],\n"d": "abc"\n}\n}'
-  (tojson(x) %==% out)
+  out = '{\n  "a": 1,\n  "b": {\n    "c": [1, 2, 3],\n    "d": "abc"\n  }\n}'
+  (.tojson(x) %==% out)
 
   x = list(c("a", "b"), 1:5, TRUE)
-  out = '[["a", "b"], [1, 2, 3, 4, 5], true]'
-  (tojson(x) %==% out)
+  out = '[\n  ["a", "b"],\n  [1, 2, 3, 4, 5],\n  true\n]'
+  (.tojson(x) %==% out)
 
-  (tojson(list('"a b"' = 'quotes "\'')) %==% '{\n"\\"a b\\"": "quotes \\"\'"\n}')
+  (.tojson(list('"a b"' = 'quotes "\'')) %==% '{\n  "\\"a b\\"": "quotes \\"\'"\n}')
 
   JS = function(x) structure(x, class = "JS_EVAL")
   x = list(a = 1:5, b = JS("function() {return true;}"))
-  out = '{\n"a": [1, 2, 3, 4, 5],\n"b": function() {return true;}\n}'
-  (tojson(x) %==% out)
+  out = '{\n  "a": [1, 2, 3, 4, 5],\n  "b": function() {return true;}\n}'
+  (.tojson(x) %==% out)
 })