Port unit.js to @flow. (#855)

* Port unit.js to @flow.

* Removed unnecesary types.

src/Parser.js

@@ -4,7 +4,7 @@ import environments from "./environments";
 import MacroExpander from "./MacroExpander";
 import symbols from "./symbols";
 import utils from "./utils";
-import units from "./units";
+import { validUnit } from "./units";
 import { cjkRegex } from "./unicodeRegexes";
 import ParseNode from "./ParseNode";
 import ParseError from "./ParseError";
@@ -813,7 +813,7 @@ class Parser {
             number: +(match[1] + match[2]), // sign + magnitude, cast to number
             unit: match[3],
         };
-        if (!units.validUnit(data)) {
+        if (!validUnit(data)) {
             throw new ParseError("Invalid unit: '" + data.unit + "'", res);
         }
         return new ParseFuncOrArgument(

src/buildHTML.js

@@ -13,7 +13,7 @@ import Style from "./Style";
 import buildCommon, { makeSpan } from "./buildCommon";
 import delimiter from "./delimiter";
 import domTree from "./domTree";
-import units from "./units";
+import { calculateSize } from "./units";
 import utils from "./utils";
 import stretchy from "./stretchy";
 
@@ -628,7 +628,7 @@ groupTypes.array = function(group, options) {
 
         let gap = 0;
         if (group.value.rowGaps[r]) {
-            gap = units.calculateSize(group.value.rowGaps[r].value, options);
+            gap = calculateSize(group.value.rowGaps[r].value, options);
             if (gap > 0) { // \@argarraycr
                 gap += arstrutDepth;
                 if (depth < gap) {
@@ -1267,11 +1267,11 @@ groupTypes.rule = function(group, options) {
     // Calculate the shift, width, and height of the rule, and account for units
     let shift = 0;
     if (group.value.shift) {
-        shift = units.calculateSize(group.value.shift, options);
+        shift = calculateSize(group.value.shift, options);
     }
 
-    const width = units.calculateSize(group.value.width, options);
-    const height = units.calculateSize(group.value.height, options);
+    const width = calculateSize(group.value.width, options);
+    const height = calculateSize(group.value.height, options);
 
     // Style the rule to the right size
     rule.style.borderRightWidth = width + "em";
@@ -1295,7 +1295,7 @@ groupTypes.kern = function(group, options) {
     const rule = makeSpan(["mord", "rule"], [], options);
 
     if (group.value.dimension) {
-        const dimension = units.calculateSize(group.value.dimension, options);
+        const dimension = calculateSize(group.value.dimension, options);
         rule.style.marginLeft = dimension + "em";
     }
 
@@ -1642,7 +1642,7 @@ groupTypes.raisebox = function(group, options) {
         }],
         size: 6,                // simulate \normalsize
     }}, options);
-    const dy = units.calculateSize(group.value.dy.value, options);
+    const dy = calculateSize(group.value.dy.value, options);
     return buildCommon.makeVList([{
         type: "elem",
         elem: body,

src/units.js

@@ -1,4 +1,4 @@
-/* eslint no-console:0 */
+// @flow
 
 /**
  * This file does conversion between units.  In particular, it provides
@@ -6,6 +6,7 @@
  */
 
 import ParseError from "./ParseError";
+import Options from "./Options";
 
 // This table gives the number of TeX pts in one of each *absolute* TeX unit.
 // Thus, multiplying a length by this number converts the length from units
@@ -36,12 +37,14 @@ const relativeUnit = {
     "mu": true,
 };
 
+export type Measurement = {number: number, unit: string};
+
 /**
  * Determine whether the specified unit (either a string defining the unit
  * or a "size" parse node containing a unit field) is valid.
  */
-const validUnit = function(unit) {
-    if (unit.unit) {
+export const validUnit = function(unit: string | Measurement): boolean {
+    if (typeof unit !== "string") {
         unit = unit.unit;
     }
     return (unit in ptPerUnit || unit in relativeUnit || unit === "ex");
@@ -52,7 +55,8 @@ const validUnit = function(unit) {
  * as parsed by functions.js argType "size") into a CSS em value for the
  * current style/scale.  `options` gives the current options.
  */
-const calculateSize = function(sizeValue, options) {
+export const calculateSize = function(
+        sizeValue: Measurement, options: Options): number {
     let scale;
     if (sizeValue.unit in ptPerUnit) {
         // Absolute units
@@ -92,8 +96,3 @@ const calculateSize = function(sizeValue, options) {
     }
     return Math.min(sizeValue.number * scale, options.maxSize);
 };
-
-module.exports = {
-    validUnit: validUnit,
-    calculateSize: calculateSize,
-};