Merge #2846 'out-of-bounds slicing'

src/nvim/api/buffer.c

@@ -108,7 +108,7 @@ ArrayOf(String) buffer_get_line_slice(Buffer buffer,
   Array rv = ARRAY_DICT_INIT;
   buf_T *buf = find_buffer_by_handle(buffer, err);
 
-  if (!buf) {
+  if (!buf || !inbounds(buf, start)) {
     return rv;
   }
 
@@ -179,6 +179,11 @@ void buffer_set_line_slice(Buffer buffer,
     return;
   }
 
+  if (!inbounds(buf, start)) {
+    api_set_error(err, Validation, _("Index out of bounds"));
+    return;
+  }
+
   start = normalize_index(buf, start) + (include_start ? 0 : 1);
   include_end = include_end || (end >= buf->b_ml.ml_line_count);
   end = normalize_index(buf, end) + (include_end ? 1 : 0);
@@ -550,3 +555,10 @@ static int64_t normalize_index(buf_T *buf, int64_t index)
   index = index > buf->b_ml.ml_line_count ? buf->b_ml.ml_line_count : index;
   return index;
 }
+
+// Returns true if the 0-indexed `index` is within the 1-indexed buffer bounds.
+static bool inbounds(buf_T *buf, int64_t index)
+{
+  linenr_T nlines = buf->b_ml.ml_line_count;
+  return index >= -nlines && index < nlines;
+}

test/functional/api/buffer_spec.lua

@@ -35,6 +35,20 @@ describe('buffer_* functions', function()
       eq('', curbuf('get_line', 0))
     end)
 
+    it('get_line: out-of-bounds returns empty string', function()
+      curbuf('set_line', 0, 'line1.a')
+      eq('', curbuf('get_line', 1))
+      eq('', curbuf('get_line', -2))
+    end)
+
+    it('set_line, del_line: out-of-bounds is an error', function()
+      curbuf('set_line', 0, 'line1.a')
+      eq(false, pcall(curbuf, 'set_line', 1, 'line1.b'))
+      eq(false, pcall(curbuf, 'set_line', -2, 'line1.b'))
+      eq(false, pcall(curbuf, 'del_line', 2))
+      eq(false, pcall(curbuf, 'del_line', -3))
+    end)
+
     it('can handle NULs', function()
       curbuf('set_line', 0, 'ab\0cd')
       eq('ab\0cd', curbuf('get_line', 0))
@@ -43,6 +57,27 @@ describe('buffer_* functions', function()
 
 
   describe('{get,set}_line_slice', function()
+    it('get_line_slice: out-of-bounds returns empty array', function()
+      curbuf('set_line_slice', 0, 0, true, true, {'a', 'b', 'c'})
+      eq({'a', 'b', 'c'}, curbuf('get_line_slice', 0, 2, true, true)) --sanity
+
+      eq({}, curbuf('get_line_slice', 2, 3, false, true))
+      eq({}, curbuf('get_line_slice', 3, 9, true, true))
+      eq({}, curbuf('get_line_slice', 3, -1, true, true))
+      eq({}, curbuf('get_line_slice', -3, -4, false, true))
+      eq({}, curbuf('get_line_slice', -4, -5, true, true))
+    end)
+
+    it('set_line_slice: out-of-bounds is an error', function()
+      curbuf('set_line_slice', 0, 0, true, true, {'a', 'b', 'c'})
+      eq({'a', 'b', 'c'}, curbuf('get_line_slice', 0, 2, true, true)) --sanity
+
+      eq({'c'}, curbuf('get_line_slice', -1, 4, true, true))
+      eq({'a', 'b', 'c'}, curbuf('get_line_slice', 0, 5, true, true))
+      eq(false, pcall(curbuf, 'set_line_slice', 4, 5, true, true, {'d'}))
+      eq(false, pcall(curbuf, 'set_line_slice', -4, -5, true, true, {'d'}))
+    end)
+
     it('works', function()
       eq({''}, curbuf('get_line_slice', 0, -1, true, true))
       -- Replace buffer