feat(provenance): record per-year denominator metadata

Updates transformations\$per_capita with the new denominator_source string,
popyear_range, and pop_source_counts. .attach_per_capita stashes
popyear_range on the result; .verb_spendrev strips the helper attr after
provenance is built.

R/provenance.R

@@ -61,9 +61,27 @@
       per_capita = list(
         applied = isTRUE(per_capita),
         denominator_source = if (isTRUE(per_capita)) {
-          "ACS 2018-2022 B01003_001 (population_acs from canonical_fips_xwalk)"
+          "Census F-33 population (per-year, from long.population)"
         } else {
           NA_character_
+        },
+        popyear_range = if (isTRUE(per_capita)) {
+          attr(result, ".popyear_range") %||% integer(0)
+        } else {
+          integer(0)
+        },
+        pop_source_counts = if (isTRUE(per_capita)) {
+          ps <- result[["pop_source"]]
+          if (is.null(ps) || length(ps) == 0L) {
+            list(census_f33 = 0L, unavailable = 0L)
+          } else {
+            list(
+              census_f33  = sum(ps == "census_f33", na.rm = TRUE),
+              unavailable = sum(ps == "unavailable", na.rm = TRUE)
+            )
+          }
+        } else {
+          NULL
         }
       ),
       inflation = list(

R/spending.R

@@ -79,6 +79,7 @@ cog_spending <- function(govid, years, category = NULL,
   prov$scope$govids_found   <- scope$found
   prov$scope$govids_missing <- scope$missing
   attr(result, "provenance") <- prov
+  attr(result, ".popyear_range") <- NULL
   result
 }
 
@@ -147,11 +148,12 @@ cog_spending <- function(govid, years, category = NULL,
   if (nrow(result) == 0L) {
     result$amt_per_capita_nominal <- numeric(0)
     result$pop_source <- character(0)
+    attr(result, ".popyear_range") <- integer(0)
     return(result)
   }
   years_lit <- paste(unique(as.integer(result$year)), collapse = ",")
   sql <- sprintf(
-    "SELECT canonical_govid, year, population
+    "SELECT canonical_govid, year, population, popyear
      FROM gov_population_yearly
      WHERE canonical_govid IN (%s)
        AND year IN (%s)",
@@ -163,7 +165,14 @@ cog_spending <- function(govid, years, category = NULL,
   result$amt_per_capita_nominal <- result$amt_nominal / result$population
   result$pop_source <- ifelse(is.na(result$population),
                               "unavailable", "census_f33")
+  py <- result$popyear[!is.na(result$popyear)]
+  attr(result, ".popyear_range") <- if (length(py) > 0L) {
+    as.integer(c(min(py), max(py)))
+  } else {
+    integer(0)
+  }
   result$population <- NULL
+  result$popyear <- NULL
   result
 }
 

tests/testthat/test-spending.R

@@ -173,3 +173,18 @@ test_that("aggregate fallback + unavailable pop produce concatenated notes", {
   expect_equal(notes[3],
                "Aggregate fallback applied; see cog_explain(); No population denominator available for this gov type")
 })
+
+test_that("provenance records per-year denominator metadata", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    r <- cog_spending("101006006", years = 2019:2020,
+                      category = "Police", per_capita = TRUE)
+    pc <- attr(r, "provenance")$transformations$per_capita
+    expect_true(pc$applied)
+    expect_match(pc$denominator_source, "Census F-33", fixed = FALSE)
+    expect_match(pc$denominator_source, "per-year", fixed = TRUE)
+    expect_equal(pc$pop_source_counts$census_f33, nrow(r))
+    expect_equal(pc$pop_source_counts$unavailable, 0L)
+    expect_equal(length(pc$popyear_range), 2L)
+  })
+})