Children print rework (#160)

Goals:

- switch logic around: prepare nodes before printing docs, try to avoid modifying printed result
- respect user's wish to have line breaks: fixes #143, fixes #117, closes #121
- generally try to be more in line with how prettier formats things

### BREAKING CHANGE
Tags are broken up differently now than before

CHANGELOG.md

@@ -1,5 +1,9 @@
 # prettier-plugin-svelte changelog
 
+## Unreleased
+
+* Rework of the tag breaking logic with the goal to be more in line with how Prettier formats HTML. This includes respecting the user's decision to have child tags in seperate lines even if they don't exceed the maximum line width ([#143](https://github.com/sveltejs/prettier-plugin-svelte/issues/143), [#117](https://github.com/sveltejs/prettier-plugin-svelte/issues/117)). This is a breaking change because tags are broken up differently now than before.
+
 ## 1.4.2
 
 * Pass options to embedded parser ([#162](https://github.com/sveltejs/prettier-plugin-svelte/issues/162))

src/embed.ts

@@ -4,9 +4,9 @@ import { snippedTagContentAttribute } from './lib/snipTagContent';
 import { PrintFn } from './print';
 import {
     getAttributeTextValue,
-    isNodeSupportedLanguage,
-    isIgnoreDirective,
     getPreviousNode,
+    isIgnoreDirective,
+    isNodeSupportedLanguage,
 } from './print/node-helpers';
 import { Node } from './print/nodes';
 

src/print/doc-helpers.ts

@@ -1,42 +1,42 @@
 import { Doc, doc } from 'prettier';
+import { findLastIndex } from './helpers';
 
-export function isLine(doc: Doc) {    
-  return typeof doc === 'object' && doc.type === 'line' 
-} 
-
-export function isLineDiscardedIfLonely(doc: Doc) {
-  return isLine(doc) && !(doc as doc.builders.Line).keepIfLonely
+export function isLine(docToCheck: Doc) {
+    return (
+        docToCheck === doc.builders.hardline ||
+        (typeof docToCheck === 'object' && docToCheck.type === 'line')
+    );
 }
 
 /**
  * Check if the doc is empty, i.e. consists of nothing more than empty strings (possibly nested).
  */
 export function isEmptyDoc(doc: Doc): boolean {
-  if (typeof doc === 'string') {
-      return doc.length === 0;
-  }
+    if (typeof doc === 'string') {
+        return doc.length === 0;
+    }
 
-  if (doc.type === 'line') {
-      return !doc.keepIfLonely;
-  }
+    if (doc.type === 'line') {
+        return !doc.keepIfLonely;
+    }
 
-  const { contents } = doc as { contents?: Doc };
+    const { contents } = doc as { contents?: Doc };
 
-  if (contents) {
-      return isEmptyDoc(contents);
-  }
+    if (contents) {
+        return isEmptyDoc(contents);
+    }
 
-  const { parts } = doc as { parts?: Doc[] };
+    const { parts } = doc as { parts?: Doc[] };
 
-  if (parts) {
-      return isEmptyGroup(parts);
-  }
+    if (parts) {
+        return isEmptyGroup(parts);
+    }
 
-  return false;
+    return false;
 }
 
 export function isEmptyGroup(group: Doc[]): boolean {
-  return !group.find(doc => !isEmptyDoc(doc))
+    return !group.find((doc) => !isEmptyDoc(doc));
 }
 
 /**
@@ -95,13 +95,3 @@ function getParts(doc: Doc): Doc[] | undefined {
         return doc.parts;
     }
 }
-
-function findLastIndex<T>(isMatch: (item: T) => boolean, items: T[]) {
-    for (let i = items.length - 1; i >= 0; i--) {
-        if (isMatch(items[i])) {
-            return i;
-        }
-    }
-
-    return -1;
-}

src/print/helpers.ts

@@ -23,3 +23,13 @@ export function isPreTagContent(path: FastPath): boolean {
 export function flatten<T>(arrays: T[][]): T[] {
     return ([] as T[]).concat.apply([], arrays);
 }
+
+export function findLastIndex<T>(isMatch: (item: T, idx: number) => boolean, items: T[]) {
+    for (let i = items.length - 1; i >= 0; i--) {
+        if (isMatch(items[i], i)) {
+            return i;
+        }
+    }
+
+    return -1;
+}