From d6358b61087bf4a9433df2c9adccf78499498002 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Alexis=20Laferri=C3=A8re?= <alexis.laf@xymus.net>
Date: Fri, 4 Sep 2015 11:46:42 -0400
Subject: [PATCH] lib/nitcc_runtime: extract `Position::underline` from
 objcwrapper
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Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
---
 contrib/objcwrapper/src/objcwrapper.nit |   10 +--------
 lib/nitcc_runtime.nit                   |   35 +++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/contrib/objcwrapper/src/objcwrapper.nit b/contrib/objcwrapper/src/objcwrapper.nit
index 418d639..28746d8 100644
--- a/contrib/objcwrapper/src/objcwrapper.nit
+++ b/contrib/objcwrapper/src/objcwrapper.nit
@@ -62,15 +62,7 @@ for src in opts.rest do
 		var pos = root.position
 		print_error "Syntax Error: {root.message}, at {pos or else ""}"
 		print_error "in {src}"
-		if pos != null then
-			var lines = content.split("\n")
-			for line in [pos.line_start..pos.line_end] do
-				print_error lines[line-1]
-			end
-
-			var ptr = " "*(pos.col_start-1).max(0) + "^"*(pos.col_end-pos.col_start)
-			print_error ptr
-		end
+		if pos != null then print_error pos.underline(content)
 		failed_parsing.add src
 		continue
 	end
diff --git a/lib/nitcc_runtime.nit b/lib/nitcc_runtime.nit
index b413c7e..bfd137d 100644
--- a/lib/nitcc_runtime.nit
+++ b/lib/nitcc_runtime.nit
@@ -296,7 +296,42 @@ class Position
 	var line_end: Int
 	var col_start: Int
 	var col_end: Int
+
 	redef fun to_s do return "{line_start}:{col_start}-{line_end}:{col_end}"
+
+	# Get the lines covered by `self` and underline the target columns.
+	#
+	# This is useful for pretty printing errors or debug the output
+	#
+	# ~~~
+	# var src = "var Foo = new Array[Int]"
+	# var pos = new Position(0,0, 1, 1, 5, 8)
+	#
+	# assert pos.underline(src) == """
+	# var Foo = new Array[Int]
+	#     ^^^"""
+	# ~~~
+	fun underline(source: Text): String
+	do
+		var res = new FlatBuffer
+
+		# All the concerned lines
+		var lines = source.split("\n")
+		for line in [line_start..line_end] do
+			res.append lines[line-1]
+			res.append "\n"
+		end
+
+		# Cover all columns, no matter their lines
+		var col_start = col_start.min(col_end)
+		var col_end = self.col_start.max(col_end)
+
+		# "           ^^^^"
+		var ptr = " "*(col_start-1).max(0) + "^"*(col_end-col_start)
+		res.append ptr
+
+		return res.to_s
+	end
 end
 
 # A node of a syntactic tree
-- 
1.7.9.5