expect_type_linter

DESCRIPTION

@@ -32,6 +32,7 @@ Suggests:
     covr,
     httr (>= 1.2.1),
     mockery,
+    patrick,
     rmarkdown,
     rstudioapi (>= 0.2),
     testthat (>= 3.0.0),
@@ -63,6 +64,7 @@ Collate:
     'exclude.R'
     'expect_lint.R'
     'expect_null_linter.R'
+    'expect_type_linter.R'
     'extract.R'
     'extraction_operator_linter.R'
     'function_left_parentheses.R'

NAMESPACE

@@ -32,6 +32,7 @@ export(equals_na_linter)
 export(expect_lint)
 export(expect_lint_free)
 export(expect_null_linter)
+export(expect_type_linter)
 export(extraction_operator_linter)
 export(function_left_parentheses_linter)
 export(get_source_expressions)
@@ -72,6 +73,7 @@ export(with_defaults)
 export(with_id)
 import(rex)
 importFrom(cyclocomp,cyclocomp)
+importFrom(glue,glue)
 importFrom(stats,na.omit)
 importFrom(utils,capture.output)
 importFrom(utils,getParseData)

R/expect_type_linter.R

@@ -0,0 +1,59 @@
+#' Require usage of expect_type(x, type) over expect_equal(typeof(x), type)
+#'
+#' [testthat::expect_type()] exists specifically for testing the storage type
+#'   of objects. [testthat::expect_equal()], [testthat::expect_identical()], and
+#'   [testthat::expect_true()] can also be used for such tests,
+#'   but it is better to use the tailored function instead.
+#'
+#' @evalRd rd_tags("expect_type_linter")
+#' @seealso [linters] for a complete list of linters available in lintr.
+#' @export
+#' @importFrom glue glue
+expect_type_linter <- function() {
+  Linter(function(source_file) {
+    if (length(source_file$parsed_content) == 0L) {
+      return(list())
+    }
+
+    xml <- source_file$xml_parsed_content
+
+    base_type_tests <- xp_text_in_table(paste0("is.", base_types))
+    xpath <- glue::glue("//expr[
+      (
+        SYMBOL_FUNCTION_CALL[text() = 'expect_equal' or text() = 'expect_identical']
+        and following-sibling::expr[1][expr[SYMBOL_FUNCTION_CALL[text() = 'typeof']]]
+      ) or (
+        SYMBOL_FUNCTION_CALL[text() = 'expect_true']
+        and following-sibling::expr[1][expr[SYMBOL_FUNCTION_CALL[ {base_type_tests} ]]]
+      )
+    ]")
+
+    bad_expr <- xml2::xml_find_all(xml, xpath)
+    return(lapply(
+      bad_expr,
+      xml_nodes_to_lint,
+      source_file = source_file,
+      message = paste(
+        "expect_type(x, t) is better than expect_equal(typeof(x), t),",
+        "expect_identical(typeof(x), t), or expect_true(is.<t>(x)).",
+        'Note that typeof(1) is "double" and typeof(function(x) x) is "closure".'
+      ),
+      type = "warning"
+    ))
+  })
+}
+
+# NB: the full list of values that can arise from `typeof(x)` is available
+#   in ?typeof (or, slightly more robustly, in the R source: src/main/util.c.
+#   Not all of them are available in is.<type> form, e.g. 'any' or
+#   'special'. 'builtin' and 'closure' are special cases, corresponding to
+#   is.primitive and is.function (essentially).
+base_types <- c(
+  "raw", "logical", "integer", "double", "complex", "character", "list",
+  "numeric", "function", "primitive", "environment", "pairlist", "promise",
+  # Per ?is.language, it's the same as is.call || is.name || is.expression.
+  #   so by blocking it, we're forcing more precise tests of one of
+  #   those directly ("language", "symbol", and "expression", resp.)
+  # NB: is.name and is.symbol are identical.
+  "language", "call", "name", "symbol", "expression"
+)

inst/lintr/linters.csv

@@ -1,44 +1,45 @@
 linter,tags
 absolute_path_linter,robustness best_practices configurable
 assignment_linter,style consistency default
+assignment_spaces_linter,style readability
 backport_linter,robustness configurable package_development
 closed_curly_linter,style readability default configurable
 commas_linter,style readability default
 commented_code_linter,style readability best_practices default
 cyclocomp_linter,style readability best_practices default configurable
+duplicate_argument_linter,correctness common_mistakes configurable
 equals_na_linter,robustness correctness common_mistakes default
 expect_null_linter,package_development best_practices
+expect_type_linter,package_development best_practices
 extraction_operator_linter,style best_practices
 function_left_parentheses_linter,style readability default
 implicit_integer_linter,style consistency best_practices
 infix_spaces_linter,style readability default
 line_length_linter,style readability default configurable
+missing_argument_linter,correctness common_mistakes configurable
+missing_package_linter,robustness common_mistakes
+namespace_linter,correctness robustness configurable
 no_tab_linter,style consistency default
 nonportable_path_linter,robustness best_practices configurable
 object_length_linter,style readability default configurable
 object_name_linter,style consistency default configurable
 object_usage_linter,style readability correctness default
 open_curly_linter,style readability default configurable
 package_hooks_linter,style correctness package_development
+paren_body_linter,style readability default
 paren_brace_linter,style readability default
+pipe_call_linter,style readability
 pipe_continuation_linter,style readability default
 semicolon_terminator_linter,style readability default configurable
 seq_linter,robustness efficiency consistency best_practices default
 single_quotes_linter,style consistency readability default
 spaces_inside_linter,style readability default
 spaces_left_parentheses_linter,style readability default
+sprintf_linter,correctness common_mistakes
 T_and_F_symbol_linter,style readability robustness consistency best_practices default
 todo_comment_linter,style configurable
 trailing_blank_lines_linter,style default
 trailing_whitespace_linter,style default
 undesirable_function_linter,style efficiency configurable robustness best_practices
 undesirable_operator_linter,style efficiency configurable robustness best_practices
 unneeded_concatenation_linter,style readability efficiency
-assignment_spaces_linter,style readability
-duplicate_argument_linter,correctness common_mistakes configurable
-missing_argument_linter,correctness common_mistakes configurable
-missing_package_linter,robustness common_mistakes
-namespace_linter,correctness robustness configurable
-paren_body_linter,style readability default
-pipe_call_linter,style readability
-sprintf_linter,correctness common_mistakes

tests/testthat.R

@@ -1,4 +1,5 @@
 library(testthat)
+library(patrick)
 library(lintr)
 
 test_check("lintr")

tests/testthat/test-expect_type_linter.R

@@ -0,0 +1,54 @@
+test_that("expect_type_linter skips allowed usages", {
+  # expect_type doesn't have an inverted version
+  expect_lint("expect_true(!is.numeric(x))", NULL, expect_type_linter())
+  # NB: also applies to tinytest, but it's sufficient to test testthat
+  expect_lint("testthat::expect_true(!is.numeric(x))", NULL, expect_type_linter)
+
+  # other is.<x> calls are not suitable for expect_type in particular
+  expect_lint("expect_true(is.data.frame(x))", NULL, expect_type_linter())
+
+  # expect_type(x, ...) cannot be cleanly used here:
+  expect_lint("expect_true(typeof(x) %in% c('builtin', 'closure'))", NULL, expect_type_linter)
+})
+
+test_that("expect_type_linter blocks simple disallowed usages", {
+  expect_lint(
+    "expect_equal(typeof(x), 'double')",
+    rex::rex("expect_type(x, t) is better than expect_equal(typeof(x), t)"),
+    expect_type_linter
+  )
+
+  # expect_identical is treated the same as expect_equal
+  expect_lint(
+    "testthat::expect_identical(typeof(x), 'language')",
+    rex::rex("expect_type(x, t) is better than expect_equal(typeof(x), t)"),
+    expect_type_linter
+  )
+
+  # different equivalent usage
+  expect_lint(
+    "expect_true(is.complex(foo(x)))",
+    rex::rex("expect_type(x, t) is better than expect_equal(typeof(x), t)"),
+    expect_type_linter
+  )
+})
+
+
+local({
+  # test for lint errors appropriately raised for all is.<type> calls
+  is_types <- c(
+    "raw", "logical", "integer", "double", "complex", "character", "list",
+    "numeric", "function", "primitive", "environment", "pairlist", "promise",
+    "language", "call", "name", "symbol", "expression"
+  )
+  patrick::with_parameters_test_that(
+    "expect_type_linter catches expect_true(is.<base type>)",
+    expect_lint(
+      sprintf("expect_true(is.%s(x))", is_type),
+      rex::rex("expect_type(x, t) is better than expect_equal(typeof(x), t)"),
+      expect_type_linter
+    ),
+    .test_name = is_types,
+    is_type = is_types
+  )
+})