Correct handling of unbraced kerns followed by spaces. (#751)

Did not realize that `Parser.nextToken.text` can contain spaces
(it can). Handle that.

src/Parser.js

@@ -789,7 +789,7 @@ Parser.prototype.parseSizeGroup = function(optional) {
     let res;
     if (!optional && this.nextToken.text !== "{") {
         res = this.parseRegexGroup(
-            /^[-+]? *(?:$|\d+|\d+\.\d*|\.\d*) *[a-z]{0,2}$/, "size");
+            /^[-+]? *(?:$|\d+|\d+\.\d*|\.\d*) *[a-z]{0,2} *$/, "size");
     } else {
         res = this.parseStringGroup("size", optional);
     }

test/katex-spec.js

@@ -1004,6 +1004,7 @@ describe("A kern parser", function() {
     const emKern = "\\kern{1em}";
     const exKern = "\\kern{1ex}";
     const muKern = "\\kern{1mu}";
+    const abKern = "a\\kern{1em}b";
     const badUnitRule = "\\kern{1px}";
     const noNumberRule = "\\kern{em}";
 
@@ -1011,10 +1012,12 @@ describe("A kern parser", function() {
         const emParse = getParsed(emKern)[0];
         const exParse = getParsed(exKern)[0];
         const muParse = getParsed(muKern)[0];
+        const abParse = getParsed(abKern)[1];
 
         expect(emParse.value.dimension.unit).toEqual("em");
         expect(exParse.value.dimension.unit).toEqual("ex");
         expect(muParse.value.dimension.unit).toEqual("mu");
+        expect(abParse.value.dimension.unit).toEqual("em");
     });
 
     it("should not parse invalid units", function() {
@@ -1037,6 +1040,9 @@ describe("A non-braced kern parser", function() {
     const emKern = "\\kern1em";
     const exKern = "\\kern 1 ex";
     const muKern = "\\kern 1mu";
+    const abKern1 = "a\\mkern1mub";
+    const abKern2 = "a\\kern-1mub";
+    const abKern3 = "a\\kern-1mu b";
     const badUnitRule = "\\kern1px";
     const noNumberRule = "\\kern em";
 
@@ -1044,10 +1050,32 @@ describe("A non-braced kern parser", function() {
         const emParse = getParsed(emKern)[0];
         const exParse = getParsed(exKern)[0];
         const muParse = getParsed(muKern)[0];
+        const abParse1 = getParsed(abKern1)[1];
+        const abParse2 = getParsed(abKern2)[1];
+        const abParse3 = getParsed(abKern3)[1];
 
         expect(emParse.value.dimension.unit).toEqual("em");
         expect(exParse.value.dimension.unit).toEqual("ex");
         expect(muParse.value.dimension.unit).toEqual("mu");
+        expect(abParse1.value.dimension.unit).toEqual("mu");
+        expect(abParse2.value.dimension.unit).toEqual("mu");
+        expect(abParse3.value.dimension.unit).toEqual("mu");
+    });
+
+    it("should parse elements on either side of a kern", function() {
+        const abParse1 = getParsed(abKern1);
+        const abParse2 = getParsed(abKern2);
+        const abParse3 = getParsed(abKern3);
+
+        expect(abParse1.length).toEqual(3);
+        expect(abParse1[0].value).toEqual("a");
+        expect(abParse1[2].value).toEqual("b");
+        expect(abParse2.length).toEqual(3);
+        expect(abParse2[0].value).toEqual("a");
+        expect(abParse2[2].value).toEqual("b");
+        expect(abParse3.length).toEqual(3);
+        expect(abParse3[0].value).toEqual("a");
+        expect(abParse3[2].value).toEqual("b");
     });
 
     it("should not parse invalid units", function() {
@@ -1064,6 +1092,16 @@ describe("A non-braced kern parser", function() {
         const parse = getParsed("\\kern+1em")[0];
         expect(parse.value.dimension.number).toBeCloseTo(1);
     });
+
+    it("should handle whitespace", function() {
+        const abKern = "a\\kern\t-\r1  \n mu\nb";
+        const abParse = getParsed(abKern);
+
+        expect(abParse.length).toEqual(3);
+        expect(abParse[0].value).toEqual("a");
+        expect(abParse[1].value.dimension.unit).toEqual("mu");
+        expect(abParse[2].value).toEqual("b");
+    });
 });
 
 describe("A left/right parser", function() {