Fix some minor issues in the English translations

README.md

@@ -456,10 +456,15 @@ would be `["during", "rain", "next-wednesday"]`.
 *   `RAIN_TYPE`
 *   `SLEET_TYPE`
 *   `SNOW_TYPE`
-*   `["parenthetical", SNOW_TYPE, SNOW_ACCUMULATION]`: For daily or weekly
-    summaries, if a significant amount of snow is expected, we will qualify it
-    with the amount of expected snow accumulation on the ground. (For example,
-    "snow (3-4 in.) throughout the day".)
+*   `["parenthetical", EXPECTED_PRECIP_TYPE, SNOW_ACCUMULATION]`: For daily or
+    weekly summaries, if a significant amount of snow is expected, we will
+    qualify it with the amount of expected snow accumulation. (For example,
+    "snow (3-4 in.) throughout the day".) PLEASE NOTE that it is possible for a
+    chance of snow accumulation to be forecasted even if the expected
+    precipitation type is rain or sleet: this may occur if the forecasted
+    temperature is right around the freezing point. Translations should clarify
+    that the parenthetical refers to a chance of snow in such circumstances.
+    (For example, "sleet (chance of 3-4 in. of snow) throughout the day".)
 
 In each of the below precipitation types, the intensity of precipitation is
 (very approximately) as follows:

lib/lang/en.js

@@ -6,26 +6,48 @@ function join_with_shared_prefix(a, b, joiner) {
 
   // HACK: This gets around "today through on Tuesday" or cases like it, which
   // are incorrect in English.
-  if(m === "today" || m === "tomorrow")
+  if(m === "today" || m === "tomorrow") {
     m = "on " + m;
+  }
 
-  while(i !== m.length &&
-        i !== b.length &&
-        m.charCodeAt(i) === b.charCodeAt(i))
+  // Skip the prefix of b that is shared with a.
+  while(
+    i !== m.length &&
+    i !== b.length &&
+    m.charCodeAt(i) === b.charCodeAt(i)
+  ) {
     ++i;
+  }
 
-  while(i && m.charCodeAt(i - 1) !== 32)
+  // ...except whitespace! We need that whitespace!
+  while(i && b.charCodeAt(i - 1) !== 32) {
     --i;
+  }
 
   return a + joiner + b.slice(i);
 }
 
 function strip_prefix(period) {
-  return period.slice(0, 9) === "overnight" ? period.slice(4) :
-    period.slice(0, 7) === "in the " ? period.slice(7) :
+  return period.startsWith("overnight")? period.slice(4):
+    period.startsWith("in the ")? period.slice(7):
       period;
 }
 
+function capitalize(str) {
+  // Do not capitalize articles, very short words, or units.
+  if(
+    str === "a" ||
+    str === "and" ||
+    str === "cm" ||
+    str === "in" ||
+    str === "of" ||
+    str === "with"
+  ) {
+    return str;
+  }
+  return str[0].toUpperCase() + str.slice(1);
+}
+
 module.exports = {
   "clear": "clear",
   "no-precipitation": "no precipitation",
@@ -104,19 +126,29 @@ module.exports = {
   "centimeters": "$1 cm.",
   "less-than": "< $1",
   "and": function(a, b) {
-    return join_with_shared_prefix(
-      a,
-      b,
-      a.indexOf(",") !== -1 ? ", and " : " and "
-    );
+    return join_with_shared_prefix(a, b, a.includes(",")? ", and ": " and ");
   },
   "through": function(a, b) {
     return join_with_shared_prefix(a, b, " through ");
   },
   "with": "$1, with $2",
   "range": "$1\u2013$2",
   "parenthetical": function(a, b) {
-    return a + " (" + b + (a === "mixed precipitation" ? " of snow)" : ")");
+    // In the case of mixed precipitation, we want to clarify that the
+    // snow accumulation in the parenthetical is snow. In the case that it's
+    // of an unknown type or rain or sleet, we want to clarify that while snow
+    // isn't expected, it has a chance of occurring. The below checks do this.
+
+    // HACK: These are not the best ways to determine the precipitation type...
+    const is_mixed = a.startsWith("mixed");
+    const is_snow = a.endsWith("flurries") || a.endsWith("snow");
+    if(!is_mixed && !is_snow) {
+      b = "with a chance of " + b;
+    }
+    if(!is_snow) {
+      b = b + " of snow";
+    }
+    return a + " (" + b + ")";
   },
   "for-hour": "$1 for the hour",
   "starting-in": "$1 starting in $2",
@@ -141,29 +173,25 @@ module.exports = {
   "temperatures-rising": "high temperatures rising to $1 $2",
   "temperatures-valleying": "high temperatures bottoming out at $1 $2",
   "temperatures-falling": "high temperatures falling to $1 $2",
-  // Capitalize the first letter of every word, except if that word is
-  // "and". (This is a very crude bastardization of proper English titling
-  // rules, but it is adequate for the purposes of this module.)
+  // Capitalize the first letter of every word except "and", "or", and units.
+  // (This is a very crude bastardization of proper English titling rules, but
+  // it is adequate for the purposes of this module.)
   "title": function(str) {
-    return str.replace(
-      /\b(?:a(?!nd\b)|c(?!m\.)|i(?!n\.)|[^\Waci])/g,
-      function(letter) {
-        return letter.toUpperCase();
-      }
-    );
+    return str.replace(/\w+/g, capitalize);
   },
-  /* Capitalize the first word of the sentence and end with a period. */
+  // Capitalize the first word of the sentence and end with a period.
   "sentence": function(str) {
-    /* Capitalize. */
-    str = str.charAt(0).toUpperCase() + str.slice(1);
+    // Capitalize.
+    str = capitalize(str);
 
-    /* Add a period if there isn't already one. */
-    if(str.charAt(str.length - 1) !== ".")
+    // Add a period if there isn't already one.
+    if(!str.endsWith(".")) {
       str += ".";
+    }
 
     return str;
   },
-  "next-hour-forecast-status": "Next hour forecasts are $1 due to $2.",
+  "next-hour-forecast-status": "next hour forecasts are $1 due to $2",
   "unavailable": "unavailable",
   "temporarily-unavailable": "temporarily unavailable",
   "partially-unavailable": "partially unavailable",

test_cases/en.json

@@ -249,6 +249,9 @@
   "Heavy Snow (3\u20135 cm.)":
     ["title", ["parenthetical", "heavy-snow", ["centimeters", ["range", 3, 5]]]],
 
+  "Rain (with a Chance of 2\u20134 in. of Snow)":
+    ["title", ["parenthetical", "medium-rain", ["inches", ["range", 2, 4]]]],
+
   "Possible Thunderstorms":
     ["title", "possible-thunderstorm"],
 
@@ -260,9 +263,11 @@
       ["starting-in", "very-light-rain", ["less-than", ["minutes", 1]]]],
 
   "Next hour forecasts are temporarily unavailable due to all nearby radar stations being offline.":
-  ["sentence",["next-hour-forecast-status", "temporarily-unavailable", "station-offline"]],
+    ["sentence", ["next-hour-forecast-status", "temporarily-unavailable", "station-offline"]],
+
   "Next hour forecasts are partially unavailable due to gaps in coverage from nearby radar stations.":
-  ["sentence",["next-hour-forecast-status", "partially-unavailable", "station-incomplete"]],
+    ["sentence", ["next-hour-forecast-status", "partially-unavailable", "station-incomplete"]],
+
   "Next hour forecasts are unavailable due to all nearby radar stations being offline.":
-  ["sentence",["next-hour-forecast-status", "unavailable", "station-offline"]]
+    ["sentence", ["next-hour-forecast-status", "unavailable", "station-offline"]]
 }