Accept all existing Greek letters using unicode characters in math mode (#410)

Test Plan:
- make test
- run screenshot tests on travis-ci

src/symbols.js

@@ -21,12 +21,16 @@ module.exports = {
     text: {},
 };
 
-function defineSymbol(mode, font, group, replace, name) {
+function defineSymbol(mode, font, group, replace, name, acceptUnicodeChar) {
     module.exports[mode][name] = {
         font: font,
         group: group,
         replace: replace,
     };
+
+    if (acceptUnicodeChar) {
+        module.exports[mode][replace] = module.exports[mode][name];
+    }
 }
 
 // Some abbreviations for commonly used strings.
@@ -413,53 +417,53 @@ defineSymbol(math, main, textord, "\u2220", "\\angle");
 defineSymbol(math, main, textord, "\u221e", "\\infty");
 defineSymbol(math, main, textord, "\u2032", "\\prime");
 defineSymbol(math, main, textord, "\u25b3", "\\triangle");
-defineSymbol(math, main, textord, "\u0393", "\\Gamma");
-defineSymbol(math, main, textord, "\u0394", "\\Delta");
-defineSymbol(math, main, textord, "\u0398", "\\Theta");
-defineSymbol(math, main, textord, "\u039b", "\\Lambda");
-defineSymbol(math, main, textord, "\u039e", "\\Xi");
-defineSymbol(math, main, textord, "\u03a0", "\\Pi");
-defineSymbol(math, main, textord, "\u03a3", "\\Sigma");
-defineSymbol(math, main, textord, "\u03a5", "\\Upsilon");
-defineSymbol(math, main, textord, "\u03a6", "\\Phi");
-defineSymbol(math, main, textord, "\u03a8", "\\Psi");
-defineSymbol(math, main, textord, "\u03a9", "\\Omega");
+defineSymbol(math, main, textord, "\u0393", "\\Gamma", true);
+defineSymbol(math, main, textord, "\u0394", "\\Delta", true);
+defineSymbol(math, main, textord, "\u0398", "\\Theta", true);
+defineSymbol(math, main, textord, "\u039b", "\\Lambda", true);
+defineSymbol(math, main, textord, "\u039e", "\\Xi", true);
+defineSymbol(math, main, textord, "\u03a0", "\\Pi", true);
+defineSymbol(math, main, textord, "\u03a3", "\\Sigma", true);
+defineSymbol(math, main, textord, "\u03a5", "\\Upsilon", true);
+defineSymbol(math, main, textord, "\u03a6", "\\Phi", true);
+defineSymbol(math, main, textord, "\u03a8", "\\Psi", true);
+defineSymbol(math, main, textord, "\u03a9", "\\Omega", true);
 defineSymbol(math, main, textord, "\u00ac", "\\neg");
 defineSymbol(math, main, textord, "\u00ac", "\\lnot");
 defineSymbol(math, main, textord, "\u22a4", "\\top");
 defineSymbol(math, main, textord, "\u22a5", "\\bot");
 defineSymbol(math, main, textord, "\u2205", "\\emptyset");
 defineSymbol(math, ams, textord, "\u2205", "\\varnothing");
-defineSymbol(math, main, mathord, "\u03b1", "\\alpha");
-defineSymbol(math, main, mathord, "\u03b2", "\\beta");
-defineSymbol(math, main, mathord, "\u03b3", "\\gamma");
-defineSymbol(math, main, mathord, "\u03b4", "\\delta");
-defineSymbol(math, main, mathord, "\u03f5", "\\epsilon");
-defineSymbol(math, main, mathord, "\u03b6", "\\zeta");
-defineSymbol(math, main, mathord, "\u03b7", "\\eta");
-defineSymbol(math, main, mathord, "\u03b8", "\\theta");
-defineSymbol(math, main, mathord, "\u03b9", "\\iota");
-defineSymbol(math, main, mathord, "\u03ba", "\\kappa");
-defineSymbol(math, main, mathord, "\u03bb", "\\lambda");
-defineSymbol(math, main, mathord, "\u03bc", "\\mu");
-defineSymbol(math, main, mathord, "\u03bd", "\\nu");
-defineSymbol(math, main, mathord, "\u03be", "\\xi");
-defineSymbol(math, main, mathord, "o", "\\omicron");
-defineSymbol(math, main, mathord, "\u03c0", "\\pi");
-defineSymbol(math, main, mathord, "\u03c1", "\\rho");
-defineSymbol(math, main, mathord, "\u03c3", "\\sigma");
-defineSymbol(math, main, mathord, "\u03c4", "\\tau");
-defineSymbol(math, main, mathord, "\u03c5", "\\upsilon");
-defineSymbol(math, main, mathord, "\u03d5", "\\phi");
-defineSymbol(math, main, mathord, "\u03c7", "\\chi");
-defineSymbol(math, main, mathord, "\u03c8", "\\psi");
-defineSymbol(math, main, mathord, "\u03c9", "\\omega");
-defineSymbol(math, main, mathord, "\u03b5", "\\varepsilon");
-defineSymbol(math, main, mathord, "\u03d1", "\\vartheta");
-defineSymbol(math, main, mathord, "\u03d6", "\\varpi");
-defineSymbol(math, main, mathord, "\u03f1", "\\varrho");
-defineSymbol(math, main, mathord, "\u03c2", "\\varsigma");
-defineSymbol(math, main, mathord, "\u03c6", "\\varphi");
+defineSymbol(math, main, mathord, "\u03b1", "\\alpha", true);
+defineSymbol(math, main, mathord, "\u03b2", "\\beta", true);
+defineSymbol(math, main, mathord, "\u03b3", "\\gamma", true);
+defineSymbol(math, main, mathord, "\u03b4", "\\delta", true);
+defineSymbol(math, main, mathord, "\u03f5", "\\epsilon", true);
+defineSymbol(math, main, mathord, "\u03b6", "\\zeta", true);
+defineSymbol(math, main, mathord, "\u03b7", "\\eta", true);
+defineSymbol(math, main, mathord, "\u03b8", "\\theta", true);
+defineSymbol(math, main, mathord, "\u03b9", "\\iota", true);
+defineSymbol(math, main, mathord, "\u03ba", "\\kappa", true);
+defineSymbol(math, main, mathord, "\u03bb", "\\lambda", true);
+defineSymbol(math, main, mathord, "\u03bc", "\\mu", true);
+defineSymbol(math, main, mathord, "\u03bd", "\\nu", true);
+defineSymbol(math, main, mathord, "\u03be", "\\xi", true);
+defineSymbol(math, main, mathord, "\u03bf", "\\omicron", true);
+defineSymbol(math, main, mathord, "\u03c0", "\\pi", true);
+defineSymbol(math, main, mathord, "\u03c1", "\\rho", true);
+defineSymbol(math, main, mathord, "\u03c3", "\\sigma", true);
+defineSymbol(math, main, mathord, "\u03c4", "\\tau", true);
+defineSymbol(math, main, mathord, "\u03c5", "\\upsilon", true);
+defineSymbol(math, main, mathord, "\u03d5", "\\phi", true);
+defineSymbol(math, main, mathord, "\u03c7", "\\chi", true);
+defineSymbol(math, main, mathord, "\u03c8", "\\psi", true);
+defineSymbol(math, main, mathord, "\u03c9", "\\omega", true);
+defineSymbol(math, main, mathord, "\u03b5", "\\varepsilon", true);
+defineSymbol(math, main, mathord, "\u03d1", "\\vartheta", true);
+defineSymbol(math, main, mathord, "\u03d6", "\\varpi", true);
+defineSymbol(math, main, mathord, "\u03f1", "\\varrho", true);
+defineSymbol(math, main, mathord, "\u03c2", "\\varsigma", true);
+defineSymbol(math, main, mathord, "\u03c6", "\\varphi", true);
 defineSymbol(math, main, bin, "\u2217", "*");
 defineSymbol(math, main, bin, "+", "+");
 defineSymbol(math, main, bin, "\u2212", "-");

test/katex-spec.js

@@ -2332,3 +2332,13 @@ describe("A parser taking String objects", function() {
         expect(new String("\\frac 1 2")).toParseLike("\\frac 1 2");
     });
 });
+
+describe("Unicode", function() {
+    it("should parse all lower case Greek letters", function() {
+        expect("αβγδεϵζηθϑικλμνξοπϖρϱςστυφϕχψω").toParse();
+    });
+
+    it("should parse 'ΓΔΘΞΠΣΦΨΩ'", function() {
+        expect("ΓΔΘΞΠΣΦΨΩ").toParse();
+    });
+});

test/screenshotter/ss_data.yaml

@@ -91,6 +91,7 @@ Gathered: |
       y = \sum_{i=1}^n i
     \end{array}
 GreekLetters: \alpha\beta\gamma\omega
+GreekUnicode: \frac{αβγδεϵζηθϑικλμνξοπϖρϱςστυφϕχψω}{ΓΔΘΞΠΣΦΨΩ\mathbf{Ω}\mathbf{\Omega}}
 GroupMacros:
     macros:
         \startExp: e^\bgroup