Sort out whitespace between text and HTML nodes (#120)

This solves the issue of whitespace either being wrongly added or removed inside inline tags or between text and tags.
Fixes #58, fixes #103, fixes #24

src/lib/elements.ts

@@ -0,0 +1,74 @@
+export type TagName = keyof HTMLElementTagNameMap | 'svg';
+
+// @see http://xahlee.info/js/html5_non-closing_tag.html
+export const selfClosingTags = [
+  'area',
+  'base',
+  'br',
+  'col',
+  'embed',
+  'hr',
+  'img',
+  'input',
+  'link',
+  'meta',
+  'param',
+  'source',
+  'track',
+  'wbr',
+];
+
+// https://developer.mozilla.org/en-US/docs/Web/HTML/Inline_elements#Elements
+export const inlineElements: TagName[] = [
+  'a',
+  'abbr',
+  'audio',
+  'b',
+  'bdi',
+  'bdo',
+  'br',
+  'button',
+  'canvas',
+  'cite',
+  'code',
+  'data',
+  'datalist',
+  'del',
+  'dfn',
+  'em',
+  'embed',
+  'i',
+  'iframe',
+  'img',
+  'input',
+  'ins',
+  'kbd',
+  'label',
+  'map',
+  'mark',
+  'meter',
+  'noscript',
+  'object',
+  'output',
+  'picture',
+  'progress',
+  'q',
+  'ruby',
+  's',
+  'samp',
+  'select',
+  'slot',
+  'small',
+  'span',
+  'strong',
+  'sub',
+  'sup',
+  'svg',
+  'template',
+  'textarea',
+  'time',
+  'u',
+  'var',
+  'video',
+  'wbr'
+];

src/print/doc-helpers.ts

@@ -0,0 +1,107 @@
+import { Doc, doc } from 'prettier';
+
+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
+}
+
+/**
+ * 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 (doc.type === 'line') {
+      return !doc.keepIfLonely;
+  }
+
+  const { contents } = doc as { contents?: Doc };
+
+  if (contents) {
+      return isEmptyDoc(contents);
+  }
+
+  const { parts } = doc as { parts?: Doc[] };
+
+  if (parts) {
+      return isEmptyGroup(parts);
+  }
+
+  return false;
+}
+
+export function isEmptyGroup(group: Doc[]): boolean {
+  return !group.find(doc => !isEmptyDoc(doc))
+}
+
+/**
+ * Trims both leading and trailing nodes matching `isWhitespace` independent of nesting level
+ * (though all trimmed adjacent nodes need to be a the same level). Modifies the `docs` array.
+ */
+export function trim(docs: Doc[], isWhitespace: (doc: Doc) => boolean): Doc[] {
+    trimLeft(docs, isWhitespace);
+    trimRight(docs, isWhitespace);
+
+    return docs;
+}
+
+/**
+ * Trims the leading nodes matching `isWhitespace` independent of nesting level (though all nodes need to be a the same level)
+ * and returnes the removed nodes.
+ */
+export function trimLeft(group: Doc[], isWhitespace: (doc: Doc) => boolean): Doc[] | undefined {
+    let firstNonWhitespace = group.findIndex((doc) => !isWhitespace(doc));
+
+    if (firstNonWhitespace < 0 && group.length) {
+        firstNonWhitespace = group.length;
+    }
+
+    if (firstNonWhitespace > 0) {
+        return group.splice(0, firstNonWhitespace);
+    } else {
+        const parts = getParts(group[0]);
+
+        if (parts) {
+            return trimLeft(parts, isWhitespace);
+        }
+    }
+}
+
+/**
+ * Trims the trailing nodes matching `isWhitespace` independent of nesting level (though all nodes need to be a the same level)
+ * and returnes the removed nodes.
+ */
+export function trimRight(group: Doc[], isWhitespace: (doc: Doc) => boolean): Doc[] | undefined {
+    let lastNonWhitespace = group.length ? findLastIndex((doc) => !isWhitespace(doc), group) : 0;
+
+    if (lastNonWhitespace < group.length - 1) {
+        return group.splice(lastNonWhitespace + 1);
+    } else {
+        const parts = getParts(group[group.length - 1]);
+
+        if (parts) {
+            return trimRight(parts, isWhitespace);
+        }
+    }
+}
+
+function getParts(doc: Doc): Doc[] | undefined {
+    if (typeof doc === 'object' && (doc.type === 'fill' || doc.type === 'concat')) {
+        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;
+}