feat: advertise 'All Categories' from cog_categories()

A reserved value nobody can discover is a trap, and this is the view
the API's /categories endpoint is built from. Emitted for the two flow
vocabularies only -- cog_balances() returns a stock and has no concept
to sum within.

Also fix test-categories.R to exclude pseudo-category rows from
crosswalk-specific assertions (one row per (category, subtype) pair,
non-empty item_codes, valid subtypes).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/testthat/test-all-categories.R

@@ -96,3 +96,30 @@ test_that('"All Categories" combines with subtype to give operating totals', {
   expect_equal(sum(ops_total$amt_nominal), sum(ops_by_cat$amt_nominal),
                tolerance = 1e-8)
 })
+
+test_that('cog_categories() advertises "All Categories" for both flows', {
+  all <- cog_categories()
+  rows <- all[all$category == "All Categories", ]
+  expect_setequal(rows$category_type, c("expenditure", "revenue"))
+  expect_true(all(is.na(rows$subtype)))
+  expect_true(all(is.na(rows$n_codes)))
+})
+
+test_that('cog_categories(type=) still scopes, including the pseudo-category', {
+  sp <- cog_categories(type = "spending")
+  expect_setequal(unique(sp$category_type), "expenditure")
+  expect_true("All Categories" %in% sp$category)
+
+  rev <- cog_categories(type = "revenue")
+  expect_setequal(unique(rev$category_type), "revenue")
+  expect_true("All Categories" %in% rev$category)
+
+  # balances have no concept vocabulary, so no pseudo-category
+  bal <- cog_categories(type = "balance")
+  expect_false("All Categories" %in% bal$category)
+})
+
+test_that('cog_categories(pattern=) matches the pseudo-category', {
+  hit <- cog_categories(pattern = "^All Categories$")
+  expect_equal(nrow(hit), 2L)
+})

tests/testthat/test-categories.R

@@ -29,7 +29,9 @@ test_that("cog_categories(type = 'spending') returns only expenditure rows", {
   # joined with the I/Q/Y flow batch -- the last two characters of Census's
   # expenditure taxonomy. `interest` is what makes the three-concept model
   # computable: primary = direct minus debt service.
-  expect_true(all(r$subtype %in%
+  # Exclude pseudo-category which has NA for subtype
+  r_crosswalk <- r[r$category != "All Categories", ]
+  expect_true(all(r_crosswalk$subtype %in%
                   c("operations", "capital", "intergovernmental", "assistance",
                     "interest", "insurance_benefits")))
 })
@@ -54,7 +56,9 @@ test_that("cog_categories(type = 'revenue') returns only revenue rows", {
   # plus the employee-retirement X codes), utility (A91-A94) and liquor store
   # (A90) revenue by definition, which is what makes both of its published
   # revenue concepts computable -- see `revenue_concept` in `?cog_revenue`.
-  expect_true(all(r$subtype %in%
+  # Exclude pseudo-category which has NA for subtype
+  r_crosswalk <- r[r$category != "All Categories", ]
+  expect_true(all(r_crosswalk$subtype %in%
                   c("own_source", "federal", "state", "local_aid",
                     "insurance_trust", "utility", "liquor_store")))
 })
@@ -69,6 +73,8 @@ test_that("cog_categories(pattern = ...) filters case-insensitively", {
 test_that("cog_categories has one row per (category, subtype)", {
   skip_if_no_corpus()
   r <- cog_categories()
+  # Exclude pseudo-category which is not a crosswalk entry
+  r <- r[r$category != "All Categories", ]
   key <- paste(r$category, r$subtype, sep = "|")
   expect_equal(length(key), length(unique(key)))
 })
@@ -76,6 +82,8 @@ test_that("cog_categories has one row per (category, subtype)", {
 test_that("cog_categories item_codes is non-empty comma-separated string", {
   skip_if_no_corpus()
   r <- cog_categories()
+  # Exclude pseudo-category which has NA for n_codes and item_codes
+  r <- r[r$category != "All Categories", ]
   expect_true(all(nzchar(r$item_codes)))
   expect_true(all(r$n_codes >= 1L))
   # n_codes should equal count of commas + 1