From c47896182a8193f705faca9ac52e07c049bd8986 Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Thu, 26 Jan 2023 18:09:54 -0600
Subject: [PATCH] Improve addition method

Fixes #286
---
 NEWS.md                       |  4 ++++
 R/glue.R                      |  9 ++++++++-
 tests/testthat/_snaps/glue.md | 11 +++++++++++
 tests/testthat/test-glue.R    | 12 ++++++++++--
 4 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 374d5a01..fd5e5d03 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,9 @@
 # glue (development version)
 
+* `+` now works in more situations, and gives errors when one side isn't a 
+  character vector. It no longer automatically applies glue interpolation to
+  both sides; you'll need to do that yourself as needed (#286).
+
 * Add `$(C_VISIBILITY)` to compiler flags to hide internal symbols from the dll (#284 @lionel-).
 
 # glue 1.6.2
diff --git a/R/glue.R b/R/glue.R
index 5df52b42..adb7a951 100644
--- a/R/glue.R
+++ b/R/glue.R
@@ -337,7 +337,14 @@ as.character.glue <- function(x, ...) {
 
 #' @export
 `+.glue` <- function(e1, e2) {
-  glue(e1, e2, .envir = parent.frame())
+  if (!is.character(e1)) {
+    stop("LHS must be a character vector.")
+  }
+  if (!is.character(e2)) {
+    stop("RHS must be a character vector.")
+  }
+
+  as_glue(paste0(e1, e2))
 }
 
 #' @importFrom methods setOldClass
diff --git a/tests/testthat/_snaps/glue.md b/tests/testthat/_snaps/glue.md
index 58bbd230..72c7de7e 100644
--- a/tests/testthat/_snaps/glue.md
+++ b/tests/testthat/_snaps/glue.md
@@ -1,3 +1,14 @@
+# + method requires character vectors
+
+    Code
+      as_glue("a") + 1
+    Error <simpleError>
+      RHS must be a character vector.
+    Code
+      1 + as_glue("a")
+    Error <simpleError>
+      LHS must be a character vector.
+
 # unterminated comment
 
     Code
diff --git a/tests/testthat/test-glue.R b/tests/testthat/test-glue.R
index af9389da..f258ed96 100644
--- a/tests/testthat/test-glue.R
+++ b/tests/testthat/test-glue.R
@@ -509,9 +509,17 @@ test_that("throws informative error if interpolating a function", {
 
 test_that("+ method for glue works", {
   expect_identical(glue("foo") + "bar", as_glue("foobar"))
+  expect_identical(glue("x = ") + "{x}", as_glue("x = {x}"))
 
-  x <- 1
-  expect_identical(glue("x = ") + "{x}", glue("x = {x}"))
+  x <- c("a", "b", "c")
+  expect_identical("(" + as_glue(x) + ")", paste0("(", x, ")"))
+})
+
+test_that("+ method requires character vectors", {
+  expect_snapshot(error = TRUE, {
+    as_glue("a") + 1
+    1 + as_glue("a")
+  })
 })
 
 test_that("unterminated quotes are error", {