From 9a3ddd7998ec2acc692c76b04398452cd9824d28 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ma=C3=ABlle=20Salmon?= <maelle.salmon@yahoo.se>
Date: Tue, 22 Jul 2025 15:40:45 +0200
Subject: [PATCH 1/3] chore: create `check_vertex()`

---
 R/aaa-auto.R                    | 132 ++++++++------------------------
 R/interface.R                   |   8 +-
 R/utils-vertex.R                |  20 +++++
 tests/testthat/_snaps/flow.md   |  16 ++--
 tests/testthat/test-interface.R |   2 +-
 tools/stimulus/types-RR.yaml    |   8 +-
 6 files changed, 66 insertions(+), 120 deletions(-)
 create mode 100644 R/utils-vertex.R

diff --git a/R/aaa-auto.R b/R/aaa-auto.R
index 1de6e7c5ff4..aa59fc9bb67 100644
--- a/R/aaa-auto.R
+++ b/R/aaa-auto.R
@@ -63,13 +63,9 @@ get_all_eids_between_impl <- function(graph, from, to, directed=TRUE) {
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(to)
   directed <- as.logical(directed)
 
   on.exit( .Call(R_igraph_finalizer) )
@@ -666,13 +662,9 @@ are_adjacent_impl <- function(graph, v1, v2) {
   # Argument checks
   ensure_igraph(graph)
   v1 <- as_igraph_vs(graph, v1)
-  if (length(v1) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(v1)
   v2 <- as_igraph_vs(graph, v2)
-  if (length(v2) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(v2)
 
   on.exit( .Call(R_igraph_finalizer) )
   # Function call
@@ -685,13 +677,9 @@ get_shortest_path_impl <- function(graph, from, to, mode=c("out", "in", "all", "
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(to)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
   on.exit( .Call(R_igraph_finalizer) )
@@ -710,13 +698,9 @@ get_shortest_path_bellman_ford_impl <- function(graph, from, to, weights=NULL, m
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(to)
   if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
     weights <- E(graph)$weight
   }
@@ -743,13 +727,9 @@ get_shortest_path_dijkstra_impl <- function(graph, from, to, weights=NULL, mode=
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(to)
   if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
     weights <- E(graph)$weight
   }
@@ -809,13 +789,9 @@ get_k_shortest_paths_impl <- function(graph, from, to, ..., k, weights=NULL, mod
   }
   k <- as.numeric(k)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(to)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
   on.exit( .Call(R_igraph_finalizer) )
@@ -834,13 +810,9 @@ get_widest_path_impl <- function(graph, from, to, weights=NULL, mode=c("out", "i
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(to)
   if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
     weights <- E(graph)$weight
   }
@@ -867,13 +839,9 @@ get_widest_paths_impl <- function(graph, from, to=V(graph), weights=NULL, mode=c
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
-    weights <- E(graph)$weight
-  }
+  check_vertex(to)
   if (!is.null(weights) && any(!is.na(weights))) {
     weights <- as.numeric(weights)
   } else {
@@ -1865,9 +1833,7 @@ pseudo_diameter_impl <- function(graph, start.vid, directed=TRUE, unconnected=TR
   # Argument checks
   ensure_igraph(graph)
   start.vid <- as_igraph_vs(graph, start.vid)
-  if (length(start.vid) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(start.vid)
   directed <- as.logical(directed)
   unconnected <- as.logical(unconnected)
 
@@ -1890,9 +1856,7 @@ pseudo_diameter_dijkstra_impl <- function(graph, weights=NULL, start.vid, direct
     weights <- NULL
   }
   start.vid <- as_igraph_vs(graph, start.vid)
-  if (length(start.vid) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(start.vid)
   directed <- as.logical(directed)
   unconnected <- as.logical(unconnected)
 
@@ -1937,9 +1901,7 @@ random_walk_impl <- function(graph, start, steps, weights=NULL, mode=c("out", "i
     weights <- NULL
   }
   start <- as_igraph_vs(graph, start)
-  if (length(start) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(start)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
   steps <- as.numeric(steps)
   stuck <- switch(igraph.match.arg(stuck), "error" = 0L, "return" = 1L)
@@ -2072,9 +2034,7 @@ bfs_simple_impl <- function(graph, root, mode=c("out", "in", "all", "total")) {
   # Argument checks
   ensure_igraph(graph)
   root <- as_igraph_vs(graph, root)
-  if (length(root) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(root)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
   on.exit( .Call(R_igraph_finalizer) )
@@ -2941,13 +2901,9 @@ maxflow_impl <- function(graph, source, target, capacity=NULL) {
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(source)
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(target)
   if (is.null(capacity) && "capacity" %in% edge_attr_names(graph)) {
     capacity <- E(graph)$capacity
   }
@@ -3016,9 +2972,7 @@ dominator_tree_impl <- function(graph, root, mode=c("out", "in", "all", "total")
   # Argument checks
   ensure_igraph(graph)
   root <- as_igraph_vs(graph, root)
-  if (length(root) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(root)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
   on.exit( .Call(R_igraph_finalizer) )
@@ -3034,13 +2988,9 @@ all_st_cuts_impl <- function(graph, source, target) {
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(source)
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(target)
 
   on.exit( .Call(R_igraph_finalizer) )
   # Function call
@@ -3058,13 +3008,9 @@ all_st_mincuts_impl <- function(graph, source, target, capacity=NULL) {
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(source)
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(target)
   if (is.null(capacity) && "capacity" %in% edge_attr_names(graph)) {
     capacity <- E(graph)$capacity
   }
@@ -3783,9 +3729,7 @@ fundamental_cycles_impl <- function(graph, start=NULL, bfs.cutoff=-1, weights=NU
   # Argument checks
   ensure_igraph(graph)
   if (!is.null(start)) start <- as_igraph_vs(graph, start)
-  if (length(start) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(start)
   bfs.cutoff <- as.numeric(bfs.cutoff)
   if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
     weights <- E(graph)$weight
@@ -3917,9 +3861,7 @@ random_spanning_tree_impl <- function(graph, vid=0) {
   # Argument checks
   ensure_igraph(graph)
   if (!is.null(vid)) vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(vid)
 
   on.exit( .Call(R_igraph_finalizer) )
   # Function call
@@ -3962,9 +3904,7 @@ deterministic_optimal_imitation_impl <- function(graph, vid, optimality=c("maxim
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(vid)
   optimality <- switch(igraph.match.arg(optimality), "minimum"=0L, "maximum"=1L)
   strategies <- as.numeric(strategies)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
@@ -4003,9 +3943,7 @@ roulette_wheel_imitation_impl <- function(graph, vid, is.local, quantities, stra
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(vid)
   is.local <- as.logical(is.local)
   strategies <- as.numeric(strategies)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
@@ -4021,9 +3959,7 @@ stochastic_imitation_impl <- function(graph, vid, algo, quantities, strategies,
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(vid)
   strategies <- as.numeric(strategies)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
@@ -4038,9 +3974,7 @@ vertex_path_from_edge_path_impl <- function(graph, start=NULL, edge.path, mode=c
   # Argument checks
   ensure_igraph(graph)
   if (!is.null(start)) start <- as_igraph_vs(graph, start)
-  if (length(start) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(start)
   edge.path <- as_igraph_es(graph, edge.path)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
diff --git a/R/interface.R b/R/interface.R
index e5317fd54ed..fcc4c83ca68 100644
--- a/R/interface.R
+++ b/R/interface.R
@@ -354,9 +354,7 @@ neighbors <- function(graph, v, mode = c("out", "in", "all", "total")) {
     mode <- switch(mode, "out" = 1, "in" = 2, "all" = 3, "total" = 3)
   }
   v <- as_igraph_vs(graph, v)
-  if (length(v) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(v)
   on.exit(.Call(R_igraph_finalizer))
   res <- .Call(R_igraph_neighbors, graph, v - 1, as.numeric(mode)) + 1L
 
@@ -393,9 +391,7 @@ incident <- function(graph, v, mode = c("all", "out", "in", "total")) {
     mode <- 1
   }
   v <- as_igraph_vs(graph, v)
-  if (length(v) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(v)
   on.exit(.Call(R_igraph_finalizer))
   res <- .Call(R_igraph_incident, graph, v - 1, as.numeric(mode)) + 1L
 
diff --git a/R/utils-vertex.R b/R/utils-vertex.R
new file mode 100644
index 00000000000..d2ad59068ea
--- /dev/null
+++ b/R/utils-vertex.R
@@ -0,0 +1,20 @@
+check_vertex <- function(arg, call = rlang::caller_env()) {
+  arg_name <- rlang::caller_arg(arg)
+  ok <- 0 ==
+    (exit_code <- .standalone_types_check_dot_call(
+      ffi_standalone_check_number_1.0.7,
+      x = arg,
+      allow_decimal = FALSE,
+      min = 0,
+      max = NULL,
+      allow_infinite = FALSE,
+      allow_na = FALSE,
+      allow_null = FALSE
+    ))
+
+  if (!ok) {
+    cli::cli_abort(
+      "Can't find vertex corresponding to {.arg {arg_name}}."
+    )
+  }
+}
diff --git a/tests/testthat/_snaps/flow.md b/tests/testthat/_snaps/flow.md
index 01e1e52f55a..2d4c8757566 100644
--- a/tests/testthat/_snaps/flow.md
+++ b/tests/testthat/_snaps/flow.md
@@ -3,32 +3,32 @@
     Code
       st_cuts(g_path, source = "a", target = NULL)
     Condition
-      Error in `st_cuts()`:
-      ! No vertex was specified
+      Error in `check_vertex()`:
+      ! Can't find vertex corresponding to `target`.
 
 ---
 
     Code
       st_cuts(g_path, source = NULL, target = "a")
     Condition
-      Error in `st_cuts()`:
-      ! No vertex was specified
+      Error in `check_vertex()`:
+      ! Can't find vertex corresponding to `source`.
 
 ---
 
     Code
       st_min_cuts(g_path, source = "a", target = NULL)
     Condition
-      Error in `st_min_cuts()`:
-      ! No vertex was specified
+      Error in `check_vertex()`:
+      ! Can't find vertex corresponding to `target`.
 
 ---
 
     Code
       st_min_cuts(g_path, source = NULL, target = "a")
     Condition
-      Error in `st_min_cuts()`:
-      ! No vertex was specified
+      Error in `check_vertex()`:
+      ! Can't find vertex corresponding to `source`.
 
 # vertex_connectivity error works
 
diff --git a/tests/testthat/test-interface.R b/tests/testthat/test-interface.R
index d1f5b10ecc1..5b36b8646ec 100644
--- a/tests/testthat/test-interface.R
+++ b/tests/testthat/test-interface.R
@@ -99,7 +99,7 @@ test_that("neighbors works", {
 
 test_that("neighbors prints an error for an empty input vector", {
   g <- make_tree(10)
-  expect_error(neighbors(g, numeric()), "No vertex was specified")
+  expect_error(neighbors(g, numeric()), "Can't find vertex")
 })
 
 
diff --git a/tools/stimulus/types-RR.yaml b/tools/stimulus/types-RR.yaml
index 35d208da901..6e0722ea675 100644
--- a/tools/stimulus/types-RR.yaml
+++ b/tools/stimulus/types-RR.yaml
@@ -97,9 +97,7 @@ VERTEX:
     CALL: '%I%-1'
     INCONV: |-
         %I% <- as_igraph_vs(%I1%, %I%)
-        if (length(%I%) == 0) {
-          stop("No vertex was specified")
-        }
+        check_vertex(%I%)
     OUTCONV:
         OUT: |-
             if (igraph_opt("return.vs.es")) {
@@ -110,9 +108,7 @@ VERTEX_ROOT:
     CALL: '%I%-1'
     INCONV: |-
         %I% <- as_igraph_vs(%I1%, %I%)
-        if (length(%I%) == 0) {
-          stop("No vertex was specified")
-        }
+        check_vertex(%I%)
     OUTCONV:
         OUT: |-
             if (igraph_opt("return.vs.es") && vcount(%I1%) != 0) {

From e036512d1ea03bd1dce73f9ebceb3671ce467b19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ma=C3=ABlle=20Salmon?= <maelle.salmon@yahoo.se>
Date: Wed, 27 Aug 2025 11:24:21 +0200
Subject: [PATCH 2/3] fix

---
 R/utils-vertex.R              | 3 ++-
 tests/testthat/_snaps/flow.md | 8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/R/utils-vertex.R b/R/utils-vertex.R
index d2ad59068ea..757a518ee97 100644
--- a/R/utils-vertex.R
+++ b/R/utils-vertex.R
@@ -14,7 +14,8 @@ check_vertex <- function(arg, call = rlang::caller_env()) {
 
   if (!ok) {
     cli::cli_abort(
-      "Can't find vertex corresponding to {.arg {arg_name}}."
+      "Can't find vertex corresponding to {.arg {arg_name}}.",
+      call = call
     )
   }
 }
diff --git a/tests/testthat/_snaps/flow.md b/tests/testthat/_snaps/flow.md
index 2d4c8757566..566deaedacd 100644
--- a/tests/testthat/_snaps/flow.md
+++ b/tests/testthat/_snaps/flow.md
@@ -3,7 +3,7 @@
     Code
       st_cuts(g_path, source = "a", target = NULL)
     Condition
-      Error in `check_vertex()`:
+      Error in `st_cuts()`:
       ! Can't find vertex corresponding to `target`.
 
 ---
@@ -11,7 +11,7 @@
     Code
       st_cuts(g_path, source = NULL, target = "a")
     Condition
-      Error in `check_vertex()`:
+      Error in `st_cuts()`:
       ! Can't find vertex corresponding to `source`.
 
 ---
@@ -19,7 +19,7 @@
     Code
       st_min_cuts(g_path, source = "a", target = NULL)
     Condition
-      Error in `check_vertex()`:
+      Error in `st_min_cuts()`:
       ! Can't find vertex corresponding to `target`.
 
 ---
@@ -27,7 +27,7 @@
     Code
       st_min_cuts(g_path, source = NULL, target = "a")
     Condition
-      Error in `check_vertex()`:
+      Error in `st_min_cuts()`:
       ! Can't find vertex corresponding to `source`.
 
 # vertex_connectivity error works

From fe4ac3de21b07e8ac87a95ed047c71863f85e6b6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ma=C3=ABlle=20Salmon?= <maelle.salmon@yahoo.se>
Date: Wed, 27 Aug 2025 11:36:16 +0200
Subject: [PATCH 3/3] yes

---
 R/aaa-auto.R | 29 +++++++----------------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/R/aaa-auto.R b/R/aaa-auto.R
index e5884d6ceab..eba1cf57637 100644
--- a/R/aaa-auto.R
+++ b/R/aaa-auto.R
@@ -952,9 +952,7 @@ get_all_shortest_paths_impl <- function(graph, from, to, mode=c("out", "in", "al
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
 
@@ -974,9 +972,7 @@ get_all_shortest_paths_dijkstra_impl <- function(graph, from, to=V(graph), weigh
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
   if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
     weights <- E(graph)$weight
@@ -1027,9 +1023,7 @@ get_all_simple_paths_impl <- function(graph, from, to=V(graph), cutoff=-1, mode=
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(from)
   to <- as_igraph_vs(graph, to)
   cutoff <- as.numeric(cutoff)
   mode <- switch(igraph.match.arg(mode), "out"=1L, "in"=2L, "all"=3L, "total"=3L)
@@ -1109,7 +1103,6 @@ get_widest_paths_impl <- function(graph, from, to=V(graph), weights=NULL, mode=c
   from <- as_igraph_vs(graph, from)
   check_vertex(from)
   to <- as_igraph_vs(graph, to)
-  check_vertex(to)
   if (is.null(weights) && "weight" %in% edge_attr_names(graph)) {
     weights <- E(graph)$weight
   }
@@ -2941,9 +2934,7 @@ layout_star_impl <- function(graph, center=V(graph)[1], order=NULL) {
   # Argument checks
   ensure_igraph(graph)
   center <- as_igraph_vs(graph, center)
-  if (length(center) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(center)
   if (!is.null(order)) order <- as.numeric(order)-1
 
   on.exit( .Call(R_igraph_finalizer) )
@@ -4041,9 +4032,7 @@ rooted_product_impl <- function(g1, g2, root) {
   ensure_igraph(g1)
   ensure_igraph(g2)
   root <- as_igraph_vs(g2, root)
-  if (length(root) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(root)
 
   on.exit( .Call(R_igraph_finalizer) )
   # Function call
@@ -4146,13 +4135,9 @@ st_mincut_impl <- function(graph, source, target, capacity=NULL) {
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(source)
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
-    stop("No vertex was specified")
-  }
+  check_vertex(target)
   if (is.null(capacity) && "capacity" %in% edge_attr_names(graph)) {
     capacity <- E(graph)$capacity
   }