Add summary function for lint objects

* Fix #260

* Shorten `summary.lints()`

Removes extra conditional.

* Clean up tests in test-methods.R

- Make the intent of the `summary.lints()` tests clearer. 
- Divide into 2 tests (no lints vs lints found).
- Use assignment linter explicitly.

* Reference summary.lints() in NEWS.md

Author: wlandau-lilly

NAMESPACE

@@ -6,6 +6,7 @@ S3method(names,lints)
 S3method(print,lint)
 S3method(print,lints)
 S3method(split,lints)
+S3method(summary,lints)
 export(Lint)
 export(T_and_F_symbol_linter)
 export(absolute_path_linter)

NEWS.md

@@ -50,6 +50,7 @@
 * Commas linter handles missing arguments calls properly (#145)
 * Add `function_left_parentheses_linter` to check that there is no space between
   a function name and its left parentheses (#204, @jrnold).
+* Implement `summary.lints()` (#260, #262, @wlandau).
 
 # lintr 1.0.1 #
 * bugfix to work with knitr 1.16.7

R/methods.R

@@ -141,3 +141,16 @@ as.data.frame.lints <- function(x, row.names = NULL, optional = FALSE, ...) {
   attributes(x) <- attrs
   x
 }
+
+#' @export
+summary.lints <- function(object, ...) {
+  filenames <- vapply(object, `[[`, character(1), "filename")
+  types <- factor(vapply(object, `[[`, character(1), "type"),
+    levels = c("style", "warning", "error"))
+  tbl <- table(filenames, types)
+  filenames <- rownames(tbl)
+  res <- as.data.frame.matrix(tbl, stringsAsFactors = FALSE, row.names = NULL)
+  res$filenames <- filenames %||% character()
+  nms <- colnames(res)
+  res[order(res$filenames), c("filenames", nms[nms != "filenames"])]
+}

tests/testthat/test-methods.R

@@ -19,7 +19,7 @@ test_that("it returns the input trimmed to the last full lint if one exists with
 })
 
 test_that("as.data.frame.lints", {
-  # A minimum lint 
+  # A minimum lint
   expect_is(
     l1 <- Lint("dummy.R",
          line_number = 1L,
@@ -28,7 +28,7 @@ test_that("as.data.frame.lints", {
          line = ""),
     "lint"
   )
-    
+
   # A larger lint
   expect_is(
     l2 <- Lint("dummy.R",
@@ -41,7 +41,7 @@ test_that("as.data.frame.lints", {
               linter = "custom_linter"),
     "lint"
   )
-  
+
   # Convert lints to data.frame
   lints <- structure(list(l1, l2), class = "lints")
   expect_is(
@@ -58,9 +58,31 @@ test_that("as.data.frame.lints", {
     line = c("", "a <- 1"),
     linter = c("", "custom_linter"),
     stringsAsFactors = FALSE)
-  
+
   expect_equal(
     df,
     exp
-  )  
+  )
 })
+
+test_that("summary.lints() works (no lints)", {
+  no_lints <- lint(
+    "x <- 1\n",
+    linters = assignment_linter)
+  no_lint_summary <- summary(no_lints)
+  expect_true(is.data.frame(no_lint_summary))
+  expect_equal(nrow(no_lint_summary), 0)
+})
+
+test_that("summary.lints() works (lints found)", {
+  has_lints <- lint(
+    "x = 1\n",
+    linters = assignment_linter)
+  has_lint_summary <- summary(has_lints)
+  expect_true(is.data.frame(has_lint_summary))
+  expect_equal(nrow(has_lint_summary), 1)
+  expect_true(has_lint_summary$style > 0)
+  expect_equal(has_lint_summary$warning, 0)
+  expect_equal(has_lint_summary$error, 0)
+})
+