Merge branch 'fix-format-zero-sigfig' into release

d3.js

@@ -530,7 +530,7 @@ var d3_format_types = {
   e: function(x, p) { return x.toExponential(p); },
   f: function(x, p) { return x.toFixed(p); },
   r: function(x, p) {
-    var n = 1 + Math.floor(1e-15 + Math.log(x) / Math.LN10);
+    var n = x ? 1 + Math.floor(1e-15 + Math.log(x) / Math.LN10) : 1;
     return d3.round(x, p - n).toFixed(Math.max(0, Math.min(20, p - n)));
   }
 };

src/core/format.js

@@ -66,7 +66,7 @@ var d3_format_types = {
   e: function(x, p) { return x.toExponential(p); },
   f: function(x, p) { return x.toFixed(p); },
   r: function(x, p) {
-    var n = 1 + Math.floor(1e-15 + Math.log(x) / Math.LN10);
+    var n = x ? 1 + Math.floor(1e-15 + Math.log(x) / Math.LN10) : 1;
     return d3.round(x, p - n).toFixed(Math.max(0, Math.min(20, p - n)));
   }
 };

test/core/format-test.js

@@ -92,6 +92,7 @@ suite.addBatch({
       assert.strictEqual(f(-1.23), "−120%");
     },
     "can round to significant digits": function(format) {
+      assert.strictEqual(format(".2r")(0), "0.0");
       assert.strictEqual(format(".1r")(0.049), "0.05");
       assert.strictEqual(format(".1r")(0.49), "0.5");
       assert.strictEqual(format(".2r")(0.449), "0.45");