Replace read_from property with data_location attribute

We are changing to an attribute so it is easier to separate:

- properties: things that are included in the datapackage.json list
- attributes: things that the frictionless functions have added to pass objects from one function to the next

Data frames do the same: `attributes(iris)`

We still remove all attributes in write_package (write_resource), so that the invisibly returned package is as written to disk

Author: peterdesmet

R/read_resource.R

@@ -50,19 +50,20 @@ read_resource <- function(package, resource_name, col_select = NULL) {
   resource <- resource(package, resource_name)
 
   # Read data directly
-  if (resource$read_from == "df") {
+  data_location <- attr(resource, "data_location")
+  if (data_location == "df") {
     df <- dplyr::as_tibble(resource$data)
 
   # Read data from data
-  } else if (resource$read_from == "data") {
+  } else if (data_location == "data") {
     df <- do.call(
       function(...) rbind.data.frame(..., stringsAsFactors = FALSE),
       resource$data
     )
     df <- dplyr::as_tibble(df)
 
   # Read data from path(s)
-  } else if (resource$read_from == "path" || resource$read_from == "url") {
+  } else if (data_location == "path" || data_location == "url") {
     df <- read_from_path(package, resource_name, col_select)
   }
   return(df)

R/resource.R

@@ -4,8 +4,8 @@
 #' described `resources`.
 #'
 #' @inheritParams read_resource
-#' @return List describing a Data Resource, with new property `read_from` to
-#'   indicate how data should be read.
+#' @return List describing a Data Resource, with new attribute `data_location`
+#'   to indicate how the data are attached.
 #'   If present, `path` will be updated to contain the full path(s).
 #' @family accessor functions
 #' @noRd
@@ -47,12 +47,12 @@ resource <- function(package, resource_name) {
     )
   }
 
-  # Assign read_from property (based on path, then df, then data)
+  # Assign data_location attribute (based on path, then df, then data)
   if (length(resource$path) != 0) {
     if (all(is_url(resource$path))) {
-      resource$read_from <- "url"
+      data_location <- "url"
     } else {
-      resource$read_from <- "path"
+      data_location <- "path"
     }
     # Expand paths to full paths, check if file exists and check path safety,
     # unless those paths were willingly added by user in add_resource()
@@ -62,10 +62,11 @@ resource <- function(package, resource_name) {
       )
     }
   } else if (is.data.frame(resource$data)) {
-    resource$read_from <- "df"
+    data_location <- "df"
   } else if (!is.null(resource$data)) {
-    resource$read_from <- "data"
+    data_location <- "data"
   }
+  attr(resource, "data_location") <- data_location
 
   return(resource)
 }

R/write_resource.R

@@ -14,7 +14,8 @@ write_resource <- function(package, resource_name, directory = ".",
   resource <- resource(package, resource_name)
 
   # Resource contains new data
-  if (resource$read_from == "df") {
+  data_location <- attr(resource, "data_location")
+  if (data_location == "df") {
     if (compress) {
       file_name <- paste(resource_name, "csv", "gz", sep = ".")
     } else {
@@ -28,15 +29,14 @@ write_resource <- function(package, resource_name, directory = ".",
     resource$mediatype <- "text/csv"
     resource$encoding <- "utf-8" # Enforced by readr::write_csv()
     resource$dialect <- NULL
-    resource$read_from <- NULL
     resource$data <- NULL
 
   # Resource originally had data property
-  } else if (resource$read_from == "data") {
-    resource$read_from <- NULL
+  } else if (data_location == "data") {
+    # Do nothing
 
   # Resource has local paths (optionally mixed with URLs)
-  } else if (resource$read_from == "path") {
+  } else if (data_location == "path") {
     # Download or copy file to directory, point path to file name (in that dir)
     # Note that existing files will not be overwritten
     out_paths <- vector()
@@ -56,14 +56,15 @@ write_resource <- function(package, resource_name, directory = ".",
       }
       out_paths <- append(out_paths, file_name)
     }
-    resource$read_from <- NULL
     resource$path <- out_paths
 
   # Resource has URL paths (only)
-  } else if (resource$read_from == "url") {
+  } else if (data_location == "url") {
     # Don't touch file, leave URL path as is
-    resource$read_from <- NULL
   }
 
+  # Remove attributes
+  attr(resource, "data_location") <- NULL
+
   return(resource)
 }

tests/testthat/test-write_package.R

@@ -333,7 +333,6 @@ test_that("write_package() sets correct properties for data frame resources", {
   expect_null(resource_written$dialect)
   expect_identical(resource_written$schema, schema)
   expect_null(resource_written$data)
-  expect_null(resource_written$read_from)
 })
 
 test_that("write_package() retains custom properties set in add_resource()", {