Develop

.github/workflows/R-CMD-check.yaml

@@ -1,50 +1,50 @@
-# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
-# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
-on:
-  push:
-    branches: [main, master]
-  pull_request:
-
-name: R-CMD-check.yaml
-
-permissions: read-all
-
-jobs:
-  R-CMD-check:
-    runs-on: ${{ matrix.config.os }}
-
-    name: ${{ matrix.config.os }} (${{ matrix.config.r }})
-
-    strategy:
-      fail-fast: false
-      matrix:
-        config:
-          - {os: macos-latest,   r: 'release'}
-          - {os: windows-latest, r: 'release'}
-          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
-          - {os: ubuntu-latest,   r: 'release'}
-          - {os: ubuntu-latest,   r: 'oldrel-1'}
-
-    env:
-      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
-      R_KEEP_PKG_SOURCE: yes
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - uses: r-lib/actions/setup-pandoc@v2
-
-      - uses: r-lib/actions/setup-r@v2
-        with:
-          r-version: ${{ matrix.config.r }}
-          http-user-agent: ${{ matrix.config.http-user-agent }}
-
-      - uses: r-lib/actions/setup-r-dependencies@v2
-        with:
-          extra-packages: any::rcmdcheck
-          needs: check
-
-      - uses: r-lib/actions/check-r-package@v2
-        with:
-          upload-snapshots: true
-          build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")'
+# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
+# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
+on:
+  push:
+    branches: [main, master, develop]
+  pull_request:
+
+name: R-CMD-check.yaml
+
+permissions: read-all
+
+jobs:
+  R-CMD-check:
+    runs-on: ${{ matrix.config.os }}
+
+    name: ${{ matrix.config.os }} (${{ matrix.config.r }})
+
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+          - {os: macos-latest,   r: 'release'}
+          - {os: windows-latest, r: 'release'}
+          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-latest,   r: 'release'}
+          - {os: ubuntu-latest,   r: 'oldrel-1'}
+
+    env:
+      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
+      R_KEEP_PKG_SOURCE: yes
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          r-version: ${{ matrix.config.r }}
+          http-user-agent: ${{ matrix.config.http-user-agent }}
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: any::rcmdcheck
+          needs: check
+
+      - uses: r-lib/actions/check-r-package@v2
+        with:
+          upload-snapshots: true
+          build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")'

DESCRIPTION

@@ -13,12 +13,15 @@ Description: The main goal is to connect to SPARQL endpoints and bering their st
 License: MIT + file LICENSE
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.3.2
 LazyData: true
 Imports:
+  S7,
   tools,
   httr2, 
   stats
 Suggests: 
     testthat (>= 3.0.0)
 Config/testthat/edition: 3
+Depends: 
+    R (>= 4.3)
+Config/roxygen2/version: 8.0.0

R/endpoint_class.R

@@ -0,0 +1,77 @@
+#' 'SPARQL' endpoint (base class)
+#'
+#' The base S7 class every endpoint backend inherits from. You will
+#' not normally call `sparql_endpoint()` directly -- use a specific
+#' constructor like `new_generic_endpoint()`.
+#'
+#' @param url Character. The SPARQL endpoint URL (the address a query
+#'   is sent to).
+#' @param name Character. A short label for the endpoint, used for
+#'   caching and messages.
+#' @param headers A named list of extra HTTP headers sent with every
+#'   request (for example a custom `User-Agent`).
+#' @param timeout Numeric. Request timeout in seconds.
+#'
+#' @export
+sparql_endpoint <- S7::new_class(
+  "sparql_endpoint",
+  properties = list(
+    url = S7::new_property(
+      S7::class_character,
+      validator = function(value) {
+        if (length(value) != 1 || !nzchar(value)) "must be a single non-empty string"
+      }
+    ),
+    name = S7::new_property(
+      S7::class_character,
+      default = quote(NA_character_),
+      validator = function(value) {
+        if (length(value) != 1) "must be a single string (or NA)"
+      }
+    ),
+    headers = S7::new_property(
+      S7::class_list,
+      default = quote(list()),
+      validator = function(value) {
+        if (length(value) > 0 && (is.null(names(value)) || any(!nzchar(names(value))))) {
+          "must be a fully named list"
+        }
+      }
+    ),
+    timeout = S7::new_property(
+      S7::class_numeric,
+      default = 60,
+      validator = function(value) {
+        if (length(value) != 1 || is.na(value) || value <= 0) "must be a single positive number"
+      }
+    )
+  )
+)
+
+#' Generic 'SPARQL' 1.1 backend
+#'
+#' The fallback backend used for any endpoint that isn't registered
+#' under a more specific class.
+#'
+#' @param url,name,headers,timeout See [sparql_endpoint()].
+#' @export
+generic_endpoint <- S7::new_class("generic_endpoint", parent = sparql_endpoint)
+
+#' Discover the classes used by an endpoint
+#' @param endpoint A `sparql_endpoint` object.
+#' @param ... Passed on to methods (commonly `limit`).
+#' @return A data frame with columns `class` and `n`.
+#' @export
+ep_classes <- S7::new_generic("ep_classes", "endpoint")
+
+#' Discover the properties (predicates) used by an endpoint
+#' @inheritParams ep_classes
+#' @return A data frame with columns `property` and `n`.
+#' @export
+ep_properties <- S7::new_generic("ep_properties", "endpoint")
+
+#' Discover which classes are linked by which properties
+#' @inheritParams ep_classes
+#' @return A data frame with columns `from_class`, `property`, `to_class`, `n`.
+#' @export
+ep_class_links <- S7::new_generic("ep_class_links", "endpoint")

R/zzz.R

@@ -0,0 +1,5 @@
+NULL
+
+.onLoad <- function(libname, pkgname) {
+  S7::methods_register()
+}

tests/testthat/test-endpoint_class.R

@@ -0,0 +1,4 @@
+test_that("sparql_endpoint validator rejects a bad url", {
+  expect_error(sparql_endpoint(url = ""))
+  expect_error(sparql_endpoint(url = c("a", "b")))
+})