Add \message, \errmessage, and \show for debugging (#2135)

* Add \message, \errmessage, and \show for debugging

* Remove unnecessary parentheses

* add tests for \message and \errmessage

src/macros.js

@@ -5,6 +5,7 @@
  */
 
 import fontMetricsData from "../submodules/katex-fonts/fontMetricsData";
+import functions from "./functions";
 import symbols from "./symbols";
 import utils from "./utils";
 import {Token} from "./Token";
@@ -300,6 +301,28 @@ defineMacro("\\newcommand", (context) => newcommand(context, false, true));
 defineMacro("\\renewcommand", (context) => newcommand(context, true, false));
 defineMacro("\\providecommand", (context) => newcommand(context, true, true));
 
+// terminal (console) tools
+defineMacro("\\message", (context) => {
+    const arg = context.consumeArgs(1)[0];
+    // eslint-disable-next-line no-console
+    console.log(arg.reverse().map(token => token.text).join(""));
+    return '';
+});
+defineMacro("\\errmessage", (context) => {
+    const arg = context.consumeArgs(1)[0];
+    // eslint-disable-next-line no-console
+    console.error(arg.reverse().map(token => token.text).join(""));
+    return '';
+});
+defineMacro("\\show", (context) => {
+    const tok = context.popToken();
+    const name = tok.text;
+    // eslint-disable-next-line no-console
+    console.log(tok, context.macros.get(name), functions[name],
+        symbols.math[name], symbols.text[name]);
+    return '';
+});
+
 //////////////////////////////////////////////////////////////////////
 // Grouping
 // \let\bgroup={ \let\egroup=}

test/katex-spec.js

@@ -3732,3 +3732,23 @@ describe("Extending katex by new fonts and symbols", function() {
         expect(katex.renderToString("۹۹^{۱۱}")).toMatchSnapshot();
     });
 });
+
+describe("debugging macros", () => {
+    describe("message", () => {
+        it("should print the argument using console.log", () => {
+            jest.spyOn(console, "log");
+            expect`\message{Hello, world}`.toParse();
+            // eslint-disable-next-line no-console
+            expect(console.log.mock.calls[0][0]).toEqual("Hello, world");
+        });
+    });
+
+    describe("errmessage", () => {
+        it("should print the argument using console.error", () => {
+            jest.spyOn(console, "error");
+            expect`\errmessage{Hello, world}`.toParse();
+            // eslint-disable-next-line no-console
+            expect(console.error.mock.calls[0][0]).toEqual("Hello, world");
+        });
+    });
+});