Advanced macro support and magic \dots (#794)

* Advanced macro support and magic \dots

* Fix \relax behavior

* Use \DOTSB in \iff, \implies, \impliedby

* Add multiple expansion test

* Implement some of @kevinbarash's comments

* More @kevinbarabash comments

* Token moved from merge

* Add type to defineMacro

* @flow

test/katex-spec.js

@@ -783,6 +783,11 @@ describe("A text parser", function() {
     it("should parse math within text group", function() {
         expect(textWithEmbeddedMath).toParse();
     });
+
+    it("should omit spaces after commands", function() {
+        expect("\\text{\\textellipsis !}")
+            .toParseLike("\\text{\\textellipsis!}");
+    });
 });
 
 describe("A color parser", function() {
@@ -2314,6 +2319,27 @@ describe("A macro expander", function() {
         compareParseTree("e^\\foo", "e^1 23", {"\\foo": "123"});
     });
 
+    it("should preserve leading spaces inside macro definition", function() {
+        compareParseTree("\\text{\\foo}", "\\text{ x}", {"\\foo": " x"});
+    });
+
+    it("should preserve leading spaces inside macro argument", function() {
+        compareParseTree("\\text{\\foo{ x}}", "\\text{ x}", {"\\foo": "#1"});
+    });
+
+    it("should ignore expanded spaces in math mode", function() {
+        compareParseTree("\\foo", "x", {"\\foo": " x"});
+    });
+
+    it("should consume spaces after macro", function() {
+        compareParseTree("\\text{\\foo }", "\\text{x}", {"\\foo": "x"});
+    });
+
+    it("should consume spaces between arguments", function() {
+        compareParseTree("\\text{\\foo 1 2}", "\\text{12end}", {"\\foo": "#1#2end"});
+        compareParseTree("\\text{\\foo {1} {2}}", "\\text{12end}", {"\\foo": "#1#2end"});
+    });
+
     it("should allow for multiple expansion", function() {
         compareParseTree("1\\foo2", "1aa2", {
             "\\foo": "\\bar\\bar",
@@ -2321,6 +2347,41 @@ describe("A macro expander", function() {
         });
     });
 
+    it("should allow for multiple expansion with argument", function() {
+        compareParseTree("1\\foo2", "12222", {
+            "\\foo": "\\bar{#1}\\bar{#1}",
+            "\\bar": "#1#1",
+        });
+    });
+
+    it("should allow for macro argument", function() {
+        compareParseTree("\\foo\\bar", "(x)", {
+            "\\foo": "(#1)",
+            "\\bar": "x",
+        });
+    });
+
+    it("should allow for space macro argument (text version)", function() {
+        compareParseTree("\\text{\\foo\\bar}", "\\text{( )}", {
+            "\\foo": "(#1)",
+            "\\bar": " ",
+        });
+    });
+
+    it("should allow for space macro argument (math version)", function() {
+        compareParseTree("\\foo\\bar", "()", {
+            "\\foo": "(#1)",
+            "\\bar": " ",
+        });
+    });
+
+    it("should allow for empty macro argument", function() {
+        compareParseTree("\\foo\\bar", "()", {
+            "\\foo": "(#1)",
+            "\\bar": "",
+        });
+    });
+
     it("should expand the \\overset macro as expected", function() {
         expect("\\overset?=").toParseLike("\\mathop{=}\\limits^{?}");
         expect("\\overset{x=y}{\sqrt{ab}}")

test/screenshotter/ss_data.yaml

@@ -77,6 +77,11 @@ DisplayMode:
 DisplayStyle: |
     {\displaystyle\sqrt{x}}{\sqrt{x}}
     {\displaystyle \frac12}{\frac12}{\displaystyle x^1_2}{x^1_2}
+Dots: |
+    \begin{array}{l}
+      \cdots;\dots+\dots\int\dots,\dots \\
+      \cdots{};\ldots+\ldots\int\ldots,\ldots
+    \end{array}
 Exponents: a^{a^a_a}_{a^a_a}
 ExtensibleArrows: |
     \begin{array}{l}