From 7baac8331ec2bbf6cf59bbe00b950eb38b923aaa Mon Sep 17 00:00:00 2001
From: taekop <taekop@naver.com>
Date: Fri, 2 Oct 2026 13:46:11 +0900
Subject: [PATCH] Respect width in ansi_collapse(style = "head") when no
 element fits

---
 NEWS.md                          |  3 +++
 R/glue.R                         |  2 +-
 tests/testthat/test-collapsing.R | 16 ++++++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/NEWS.md b/NEWS.md
index 1de8df2fe..2731f85b2 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -40,6 +40,9 @@
 
 * Fix issues with `ansi_strwrap()` having `\r` in the string (#667)
 
+* `ansi_collapse(style = "head")` no longer exceeds `width` when not even
+  the first element fits (#570, @taekop).
+
 # cli 3.6.6
 
 * New `{.num}` and `{.bytes}` inline styles to format numbers
diff --git a/R/glue.R b/R/glue.R
index 84b2b6db9..fefd9d70c 100644
--- a/R/glue.R
+++ b/R/glue.R
@@ -245,7 +245,7 @@ collapse_head <- function(x, sep, sep2, last, trunc, width, ellipsis) {
     } else if (well == width) {
       return(ellipsis)
     } else if (well + wsep >= width) {
-      return(paste0(ansi_strtrim(x[1L], width, ellipsis = ""), ellipsis))
+      return(paste0(ansi_strtrim(x[1L], width - well, ellipsis = ""), ellipsis))
     } else {
       return(paste0(
         ansi_strtrim(x[1L], max(width - well - wsep, 0L), ellipsis = ellipsis),
diff --git a/tests/testthat/test-collapsing.R b/tests/testthat/test-collapsing.R
index 0ae11c2b8..4b9e6fdc8 100644
--- a/tests/testthat/test-collapsing.R
+++ b/tests/testthat/test-collapsing.R
@@ -189,6 +189,22 @@ test_that("ansi_collapse with width trimming", {
   })
 })
 
+test_that("ansi_collapse with style = 'head' never exceeds width (#570)", {
+  x <- c("loooooooong", "healthy live the Penguin")
+  expect_equal(ansi_collapse(x, width = 4, style = "head"), "l...")
+  expect_equal(ansi_collapse(x, width = 5, style = "head"), "lo...")
+  expect_equal(
+    ansi_collapse(x, width = 2, style = "head", ellipsis = "\u2026"),
+    "l\u2026"
+  )
+  for (width in 0:30) {
+    expect_lte(
+      ansi_nchar(ansi_collapse(x, width = width, style = "head")),
+      width
+    )
+  }
+})
+
 test_that("ansi_collapse produces consistent truncation results", {
   expect_equal(
     ansi_collapse(1:2, trunc = 1, style = "head"),