src/nodes/strings.js in prettier-0.15.1 vs src/nodes/strings.js in prettier-0.16.0

@@ -2,11 +2,12 @@
   concat,
   group,
   hardline,
   indent,
   literalline,
-  softline
+  softline,
+  join
 } = require("../prettier");
 const { concatBody, empty, makeList, prefix, surround } = require("../utils");
 const escapePattern = require("../escapePattern");
 
 // If there is some part of this string that matches an escape sequence or that
@@ -36,17 +37,18 @@
   return preferSingleQuotes && isSingleQuotable(string) ? "'" : '"';
 };
 
 const quotePattern = new RegExp("\\\\([\\s\\S])|(['\"])", "g");
 
-const makeString = (content, enclosingQuote) => {
+const makeString = (content, enclosingQuote, originalQuote) => {
+  const replaceOther = ["'", '"'].includes(originalQuote);
   const otherQuote = enclosingQuote === '"' ? "'" : '"';
 
   // Escape and unescape single and double quotes as needed to be able to
   // enclose `content` with `enclosingQuote`.
   return content.replace(quotePattern, (match, escaped, quote) => {
-    if (escaped === otherQuote) {
+    if (replaceOther && escaped === otherQuote) {
       return escaped;
     }
 
     if (quote === enclosingQuote) {
       return `\\${quote}`;
@@ -58,10 +60,57 @@
 
     return `\\${escaped}`;
   });
 };
 
+// The `parts` argument that comes into this function is an array of either
+// printed embedded expressions or plain strings (that themselves can contain
+// newlines). What we want to return is an array where each element represents a
+// line in the original text. So we end up tracking every line as we go and
+// pushing onto a `currentLine` variable, then when we hit a new line we push
+// the current line onto the `lines` variable until we've used up every part.
+const makeHeredocLines = parts => {
+  let lines = [];
+  let currentLine = [];
+
+  parts.forEach(part => {
+    if (part.type === "group" || !part.includes("\n")) {
+      // In this case we've either hit an embedded expression or the piece of
+      // the current line that we're looking at is in the middle of two of them,
+      // so we just push onto the current line and continue on.
+      currentLine.push(part);
+      return;
+    }
+
+    let splits = part.split("\n");
+    if (splits[splits.length - 1] === "") {
+      // If a line ends with a newline, then we end up with an empty string at
+      // the end of the splits, we just pop it off here since we'll handle the
+      // newlines later.
+      splits = splits.slice(0, -1);
+    }
+
+    if (currentLine.length > 0) {
+      lines.push(concat(currentLine.concat(splits[0])));
+      currentLine = [];
+    } else {
+      lines.push(splits[0]);
+    }
+
+    if (splits.length > 1) {
+      lines = lines.concat(splits.slice(1, -1));
+      currentLine.push(splits[splits.length - 1]);
+    }
+  });
+
+  if (currentLine.length > 0) {
+    lines = lines.concat(currentLine);
+  }
+
+  return lines;
+};
+
 module.exports = {
   "@CHAR": (path, { preferSingleQuotes }, _print) => {
     const { body } = path.getValue();
 
     if (body.length !== 2) {
@@ -76,14 +125,17 @@
 
     return concat([":", quote, concat(path.call(print, "body", 0)), quote]);
   },
   heredoc: (path, opts, print) => {
     const { beging, ending } = path.getValue();
+    const lines = makeHeredocLines(path.map(print, "body"));
 
     return concat([
       beging,
-      concat([literalline].concat(path.map(print, "body"))),
+      literalline,
+      join(literalline, lines),
+      literalline,
       ending
     ]);
   },
   string: makeList,
   string_concat: (path, opts, print) =>
@@ -128,10 +180,10 @@
     const parts = [];
 
     string.body.forEach((part, index) => {
       if (part.type === "@tstring_content") {
         // In this case, the part of the string is just regular string content
-        parts.push(makeString(part.body, quote));
+        parts.push(makeString(part.body, quote, string.quote));
       } else {
         // In this case, the part of the string is an embedded expression
         parts.push(path.call(print, "body", 0, "body", index));
       }
     });