Don't evaluate (title) annotations

NEWS.md

@@ -276,6 +276,10 @@ Theme fixes:
 - `plt(..., ann = FALSE)` correctly turns off title annotations now, fixing a
   regression that we missed from at least v0.6.0. Thanks to @bastistician for
   the report. (#641 @zeileis)
+- Fixed `bquote()` (and other unevaluated language) annotations such as `main`,
+  `sub`, `cap`, `xlab`, and `ylab` being evaluated instead of coerced to
+  plotmath expressions, e.g. `plt(0, 0, main = bquote(foo == .(pi)))`. Thanks 
+  (again) to @bastistician for the report. (#642 @grantmcdermott)
 
 ## v0.6.1
 

R/title.R

@@ -68,7 +68,7 @@ draw_title = function(main, sub, cap, xlab, ylab, legend, legend_args, opar,
       las = 1
     )
     args = Filter(function(x) !is.null(x), args)
-    do.call(mtext, args)
+    do.call(mtext, args, quote = TRUE)
   }
 
   if (!is.null(main)) {
@@ -88,7 +88,7 @@ draw_title = function(main, sub, cap, xlab, ylab, legend, legend_args, opar,
       font.main = get_tpar("font.main", 2),
       adj = get_tpar(c("adj.main", "adj"), 3))
     args = Filter(function(x) !is.null(x), args)
-    do.call(title, args)
+    do.call(title, args, quote = TRUE)
     par(xpd = .oxpd)
   }
 
@@ -111,7 +111,7 @@ draw_title = function(main, sub, cap, xlab, ylab, legend, legend_args, opar,
       las = 1
     )
     args = Filter(function(x) !is.null(x), args)
-    do.call(mtext, args)
+    do.call(mtext, args, quote = TRUE)
   }
 
   # Axis titles. For multi-line labels, base R places line 1 at
@@ -138,7 +138,7 @@ draw_title = function(main, sub, cap, xlab, ylab, legend, legend_args, opar,
   }
   args[["adj"]] = get_tpar(c("adj.xlab", "adj"))
   args[["cex.lab"]] = cex_xlab
-  do.call(title, args)
+  do.call(title, args, quote = TRUE)
 
   # ylab: base R already places multi-line text correctly (outermost line at
   # mgp[1], subsequent lines closer to the plot), so no line shift needed.
@@ -149,5 +149,5 @@ draw_title = function(main, sub, cap, xlab, ylab, legend, legend_args, opar,
   }
   args[["adj"]] = get_tpar(c("adj.ylab", "adj"))
   args[["cex.lab"]] = cex_ylab
-  do.call(title, args)
+  do.call(title, args, quote = TRUE)
 }

inst/tinytest/test-misc.R

@@ -153,4 +153,28 @@ expect_snapshot_plot(f, label = "formula_y1_cust_lab")
 f = function() {
   plt(0, 0, ann = FALSE)
 }
-expect_snapshot_plot(f, label = "ann=FALSE")
+expect_snapshot_plot(f, label = "ann=FALSE")
+
+
+# bquote() and other unevaluated/language annotations must be coerced
+# to plotmath expressions, not evaluated. (#624)
+
+f = function() {
+  plt(0, 0, type = "n", main = bquote(pi == .(pi)))
+}
+expect_snapshot_plot(f, label = "titles-bquote-pi")
+
+# kitchen sink: every annotation slot a (different) language object at once
+f = function() {
+  plt(
+    0, 0,
+    type = "n",
+    main = bquote(pi == .(round(pi, 2))),
+    sub  = bquote(n == .(42L)),
+    xlab = bquote(x[i]^2),
+    ylab = bquote(sqrt(y)),
+    cap  = bquote(italic("source: foo")),
+    theme = "dynamic"
+  )
+}
+expect_snapshot_plot(f, label = "titles-bquote-kitchen")