plotly · cpsievert · Jun 3, 2023 · Apr 9, 2023 · Apr 9, 2023 · Apr 9, 2023
diff --git a/R/layers2traces.R b/R/layers2traces.R
@@ -445,7 +445,9 @@ to_basic.GeomHline <- function(data, prestats_data, layout, params, p, ...) {
     data = layout$layout, cols = paste0(x, c("_min", "_max")), values_to = x, names_to = "variable"
   ) 
   lay <- as.data.frame(lay)
-  data <- merge(lay[c("PANEL", x)], data, by = "PANEL")
+  if (nrow(data) > 0) {
+    data <- merge(lay[c("PANEL", x)], data, by = "PANEL")
+  }
   data[["x"]] <- data[[x]]
   data[["y"]] <- data$yintercept
   prefix_class(data, c("GeomHline", "GeomPath"))
@@ -462,7 +464,10 @@ to_basic.GeomVline <- function(data, prestats_data, layout, params, p, ...) {
     data = layout$layout, cols = paste0(y, c("_min", "_max")), values_to = y, names_to = "variable"
   ) 
   lay <- as.data.frame(lay)
-  data <- merge(lay[c("PANEL", y)], data, by = "PANEL")
+  # fix for #1947; applied to Hline as well
+  if (nrow(data) > 0) {
+    data <- merge(lay[c("PANEL", y)], data, by = "PANEL")
+  }
   data[["y"]] <- data[[y]]
   data[["x"]] <- data$xintercept
   prefix_class(data, c("GeomVline", "GeomPath"))

diff --git a/tests/testthat/test-ggplot-hline.R b/tests/testthat/test-ggplot-hline.R
@@ -97,3 +97,38 @@ test_that("hline works with coord_flip", {
   expect_equivalent(l$data[[2]]$x, c(5, 5))
   expect_equivalent(l$data[[2]]$y, c(5.95, 6.05))
 })
+
+# fix for issue #1974 pull request #2252
+test_that("geom_vline/geom_hline does not throw an error with ggplotly when no lines are found", {
+  set.seed(123)
+  x <- seq(0, 10, by = 1)
+  # random walk
+  y <- cumsum(rnorm(length(x), mean = 0, sd = 1))
+  df <- data.frame(x, y)
+  df$value_of_interest <- "not_voi"
+  df[round(df$x, 0) == 2, ]$value_of_interest <- "voi" # value of interest
+
+  # horizontal line no error
+  p3 <- ggplot2::ggplot(df) +
+    ggplot2::geom_line(ggplot2::aes(x = x, y = y)) +
+    ggplot2::geom_hline(
+      ggplot2::aes(yintercept = x),
+      data = df[df$value_of_interest == "voi", ],
+      colour = "pink"
+    )
+
+  expect_error(plotly::ggplotly(p3), NA) # lines are found no error is thrown
+
+  # horizontal line not set; error
+  p4 <- ggplot2::ggplot(df) +
+    ggplot2::geom_line(ggplot2::aes(x = x, y = y)) +
+    ggplot2::geom_hline(
+      ggplot2::aes(yintercept = x),
+      data = df[df$value_of_interest == "something_not_matched", ],
+      colour = "pink"
+    )
+
+  # error given without fix:
+  # "Error in fix.by(by.y, y) : 'by' must specify a uniquely valid column"
+  expect_error(plotly::ggplotly(p4), NA) # no lines are found no error is thrown
+})
diff --git a/tests/testthat/test-ggplot-vline.R b/tests/testthat/test-ggplot-vline.R
@@ -46,3 +46,40 @@ test_that("vline works with coord_flip", {
   expect_equivalent(l$data[[2]]$x, c(5.95, 6.05))
   expect_equivalent(l$data[[2]]$y, c(5, 5))
 })
+
+
+# fix for issue #1974 pull request #2252
+test_that("geom_vline/geom_hline does not throw an error with ggplotly when no lines are found", {
+  set.seed(123)
+  x <- seq(0, 10, by = 1)
+  # random walk
+  y <- cumsum(rnorm(length(x), mean = 0, sd = 1))
+  df <- data.frame(x, y)
+  df$point_of_interest <- "not_poi"
+  df[df$x == 2, ]$point_of_interest <- "poi" # point of interest
+
+  # Case 1: Vertical line by feeding data to it; this allows for programmatically setting many lines at different years
+  p1 <- ggplot2::ggplot(df) +
+    ggplot2::geom_line(ggplot2::aes(x = x, y = y)) +
+    ggplot2::geom_vline(
+      ggplot2::aes(xintercept = x),
+      data = df[df$point_of_interest == "poi", ],
+      colour = "yellow"
+    )
+
+  # Test that ggplotly does not throw an error for both cases
+  expect_error(plotly::ggplotly(p1), NA) # lines are found no error is thrown
+
+  # Case 2: No lines are found, ggplot2 accepts it and no error is thrown
+  p2 <- ggplot2::ggplot(df) +
+    ggplot2::geom_line(ggplot2::aes(x = x, y = y)) +
+    ggplot2::geom_vline(
+      ggplot2::aes(xintercept = x),
+      data = df[df$point_of_interest == "something_not_matched", ],
+      colour = "yellow"
+    )
+
+  # error given without fix:
+  # "Error in fix.by(by.y, y) : 'by' must specify a uniquely valid column"
+  expect_error(plotly::ggplotly(p2), NA) # no lines are found no error is thrown
+})