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feat(compiler): Parse and recover on incomplete opening HTML tags (#38681) 

Let's say we have a code like

```html
<div<span>123</span>
```

Currently this gets parsed into a tree with the element tag `div<span`.
This has at least two downsides:

- An incorrect diagnostic that `</span>` doesn't close an element is
  emitted.
- A consumer of the parse tree using it for editor services is unable to
  provide correct completions for the opening `<span>` tag.

This patch attempts to fix both issues by instead parsing the code into
the same tree that would be parsed for `<div></div><span>123</span>`.

In particular, we do this by optimistically scanning an open tag as
usual, but if we do not notice a terminating '>', we mark the tag as
"incomplete". A parser then emits an error for the incomplete tag and
adds a synthetic (recovered) element node to the tree with the
incomplete open tag's name.

What's the downside of this? For one, a breaking change.

<ol>
<li>

The first breaking change is that `<` symbols that are ambiguously text
or opening tags will be parsed as opening tags instead of text in
element bodies. Take the code

```html
<p>a<b</p>
```

Clearly we cannot have the best of both worlds, and this patch chooses
to swap the parsing strategy to support the new feature. Of course, `<`
can still be inserted as text via the `&lt;` entity.

</li>
</ol>

Part of #38596

PR Close #38681
This commit is contained in:
Ayaz Hafiz 2020-09-02 10:17:01 -05:00 committed by Misko Hevery
parent 49f27e31ed
commit 6ae3b68acf
4 changed files with 153 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
packages/compiler/src/ml_parser/lexer.ts
View File

@ -17,6 +17,7 @@ export enum TokenType {
TAG_OPEN_END,
TAG_OPEN_END_VOID,
TAG_CLOSE,
INCOMPLETE_TAG_OPEN,
TEXT,
ESCAPABLE_RAW_TEXT,
RAW_TEXT,
@ -511,8 +512,6 @@ class _Tokenizer {
let tagName: string;
let prefix: string;
let openTagToken: Token|undefined;
let tokensBeforeTagOpen = this.tokens.length;
const innerStart = this._cursor.clone();
try {
if (!chars.isAsciiLetter(this._cursor.peek())) {
throw this._createError(
@ -523,7 +522,8 @@ class _Tokenizer {
prefix = openTagToken.parts[0];
tagName = openTagToken.parts[1];
this._attemptCharCodeUntilFn(isNotWhitespace);
while (this._cursor.peek() !== chars.$SLASH && this._cursor.peek() !== chars.$GT) {
while (this._cursor.peek() !== chars.$SLASH && this._cursor.peek() !== chars.$GT &&
this._cursor.peek() !== chars.$LT) {
this._consumeAttributeName();
this._attemptCharCodeUntilFn(isNotWhitespace);
if (this._attemptCharCode(chars.$EQ)) {
@ -535,14 +535,15 @@ class _Tokenizer {
this._consumeTagOpenEnd();
} catch (e) {
if (e instanceof _ControlFlowError) {
// When the start tag is invalid (including invalid "attributes"), assume we want a "<"
this._cursor = innerStart;
if (openTagToken) {
this.tokens.length = tokensBeforeTagOpen;
}
// Back to back text tokens are merged at the end
// We errored before we could close the opening tag, so it is incomplete.
openTagToken.type = TokenType.INCOMPLETE_TAG_OPEN;
} else {
// When the start tag is invalid, assume we want a "<" as text.
// Back to back text tokens are merged at the end.
this._beginToken(TokenType.TEXT, start);
this._endToken(['<']);
}
return;
}
@ -772,8 +773,8 @@ function isNotWhitespace(code: number): boolean {
}
function isNameEnd(code: number): boolean {
return chars.isWhitespace(code) || code === chars.$GT || code === chars.$SLASH ||
code === chars.$SQ || code === chars.$DQ || code === chars.$EQ;
return chars.isWhitespace(code) || code === chars.$GT || code === chars.$LT ||
code === chars.$SLASH || code === chars.$SQ || code === chars.$DQ || code === chars.$EQ;
}
function isPrefixEnd(code: number): boolean {

22
packages/compiler/src/ml_parser/parser.ts
View File

@ -56,7 +56,8 @@ class _TreeBuilder {
build(): void {
while (this._peek.type !== lex.TokenType.EOF) {
if (this._peek.type === lex.TokenType.TAG_OPEN_START) {
if (this._peek.type === lex.TokenType.TAG_OPEN_START ||
this._peek.type === lex.TokenType.INCOMPLETE_TAG_OPEN) {
this._consumeStartTag(this._advance());
} else if (this._peek.type === lex.TokenType.TAG_CLOSE) {
this._consumeEndTag(this._advance());
@ -233,8 +234,7 @@ class _TreeBuilder {
}
private _consumeStartTag(startTagToken: lex.Token) {
const prefix = startTagToken.parts[0];
const name = startTagToken.parts[1];
const [prefix, name] = startTagToken.parts;
const attrs: html.Attribute[] = [];
while (this._peek.type === lex.TokenType.ATTR_NAME) {
attrs.push(this._consumeAttr(this._advance()));
@ -266,6 +266,12 @@ class _TreeBuilder {
// Elements that are self-closed have their `endSourceSpan` set to the full span, as the
// element start tag also represents the end tag.
this._popElement(fullName, span);
} else if (startTagToken.type === lex.TokenType.INCOMPLETE_TAG_OPEN) {
// We already know the opening tag is not complete, so it is unlikely it has a corresponding
// close tag. Let's optimistically parse it as a full element and emit an error.
this._popElement(fullName, null);
this.errors.push(
TreeError.create(fullName, span, `Opening tag "${fullName}" not terminated.`));
}
}
@ -295,7 +301,13 @@ class _TreeBuilder {
}
}
private _popElement(fullName: string, endSourceSpan: ParseSourceSpan): boolean {
/**
* Closes the nearest element with the tag name `fullName` in the parse tree.
* `endSourceSpan` is the span of the closing tag, or null if the element does
* not have a closing tag (for example, this happens when an incomplete
* opening tag is recovered).
*/
private _popElement(fullName: string, endSourceSpan: ParseSourceSpan|null): boolean {
for (let stackIndex = this._elementStack.length - 1; stackIndex >= 0; stackIndex--) {
const el = this._elementStack[stackIndex];
if (el.name == fullName) {
@ -303,7 +315,7 @@ class _TreeBuilder {
// removed from the element stack at this point are closed implicitly, so they won't get
// an end source span (as there is no explicit closing element).
el.endSourceSpan = endSourceSpan;
el.sourceSpan.end = endSourceSpan.end || el.sourceSpan.end;
el.sourceSpan.end = endSourceSpan !== null ? endSourceSpan.end : el.sourceSpan.end;
this._elementStack.splice(stackIndex, this._elementStack.length - stackIndex);
return true;

62
packages/compiler/test/ml_parser/html_parser_spec.ts
View File

@ -11,7 +11,7 @@ import {HtmlParser, ParseTreeResult, TreeError} from '../../src/ml_parser/html_p
import {TokenType} from '../../src/ml_parser/lexer';
import {ParseError} from '../../src/parse_util';
import {humanizeDom, humanizeDomSourceSpans, humanizeLineColumn} from './ast_spec_utils';
import {humanizeDom, humanizeDomSourceSpans, humanizeLineColumn, humanizeNodes} from './ast_spec_utils';
{
describe('HtmlParser', () => {
@ -622,7 +622,7 @@ import {humanizeDom, humanizeDomSourceSpans, humanizeLineColumn} from './ast_spe
`{a, select, b {foo} % { bar {% bar}}`, 'TestComp', {tokenizeExpansionForms: true});
expect(humanizeErrors(p.errors)).toEqual([
[
6,
TokenType.RAW_TEXT,
'Unexpected character "EOF" (Do you have an unescaped "{" in your template? Use "{{ \'{\' }}") to escape it.)',
'0:36'
],
@ -840,14 +840,66 @@ import {humanizeDom, humanizeDomSourceSpans, humanizeLineColumn} from './ast_spe
]]);
});
describe('incomplete element tag', () => {
it('should parse and report incomplete tags after the tag name', () => {
const {errors, rootNodes} = parser.parse('<div<span><div </span>', 'TestComp');
expect(humanizeNodes(rootNodes, true)).toEqual([
[html.Element, 'div', 0, '<div', '<div', null],
[html.Element, 'span', 0, '<span><div </span>', '<span>', '</span>'],
[html.Element, 'div', 1, '<div ', '<div ', null],
]);
expect(humanizeErrors(errors)).toEqual([
['div', 'Opening tag "div" not terminated.', '0:0'],
['div', 'Opening tag "div" not terminated.', '0:10'],
]);
});
it('should parse and report incomplete tags after attribute', () => {
const {errors, rootNodes} =
parser.parse('<div class="hi" sty<span></span>', 'TestComp');
expect(humanizeNodes(rootNodes, true)).toEqual([
[html.Element, 'div', 0, '<div class="hi" sty', '<div class="hi" sty', null],
[html.Attribute, 'class', 'hi', 'class="hi"'],
[html.Attribute, 'sty', '', 'sty'],
[html.Element, 'span', 0, '<span></span>', '<span>', '</span>'],
]);
expect(humanizeErrors(errors)).toEqual([
['div', 'Opening tag "div" not terminated.', '0:0'],
]);
});
it('should parse and report incomplete tags after quote', () => {
const {errors, rootNodes} = parser.parse('<div "<span></span>', 'TestComp');
expect(humanizeNodes(rootNodes, true)).toEqual([
[html.Element, 'div', 0, '<div ', '<div ', null],
[html.Text, '"', 0, '"'],
[html.Element, 'span', 0, '<span></span>', '<span>', '</span>'],
]);
expect(humanizeErrors(errors)).toEqual([
['div', 'Opening tag "div" not terminated.', '0:0'],
]);
});
it('should report subsequent open tags without proper close tag', () => {
const errors = parser.parse('<div</div>', 'TestComp').errors;
expect(errors.length).toEqual(1);
expect(humanizeErrors(errors)).toEqual([[
expect(errors.length).toEqual(2);
expect(humanizeErrors(errors)).toEqual([
['div', 'Opening tag "div" not terminated.', '0:0'],
// TODO(ayazhafiz): the following error is unnecessary and can be pruned if we keep
// track of the incomplete tag names.
[
'div',
'Unexpected closing tag "div". It may happen when the tag has already been closed by another tag. For more info see https://www.w3.org/TR/html5/syntax.html#closing-elements-that-have-implied-end-tags',
'0:4'
]]);
]
]);
});
});
it('should report closing tag for void elements', () => {

68
packages/compiler/test/ml_parser/lexer_spec.ts
View File

@ -232,6 +232,45 @@ import {ParseLocation, ParseSourceFile, ParseSourceSpan} from '../../src/parse_u
[lex.TokenType.EOF, ''],
]);
});
describe('tags', () => {
it('after tag name', () => {
expect(tokenizeAndHumanizeSourceSpans('<div<span><div</span>')).toEqual([
[lex.TokenType.INCOMPLETE_TAG_OPEN, '<div'],
[lex.TokenType.TAG_OPEN_START, '<span'],
[lex.TokenType.TAG_OPEN_END, '>'],
[lex.TokenType.INCOMPLETE_TAG_OPEN, '<div'],
[lex.TokenType.TAG_CLOSE, '</span>'],
[lex.TokenType.EOF, ''],
]);
});
it('in attribute', () => {
expect(tokenizeAndHumanizeSourceSpans('<div class="hi" sty<span></span>')).toEqual([
[lex.TokenType.INCOMPLETE_TAG_OPEN, '<div'],
[lex.TokenType.ATTR_NAME, 'class'],
[lex.TokenType.ATTR_QUOTE, '"'],
[lex.TokenType.ATTR_VALUE, 'hi'],
[lex.TokenType.ATTR_QUOTE, '"'],
[lex.TokenType.ATTR_NAME, 'sty'],
[lex.TokenType.TAG_OPEN_START, '<span'],
[lex.TokenType.TAG_OPEN_END, '>'],
[lex.TokenType.TAG_CLOSE, '</span>'],
[lex.TokenType.EOF, ''],
]);
});
it('after quote', () => {
expect(tokenizeAndHumanizeSourceSpans('<div "<span></span>')).toEqual([
[lex.TokenType.INCOMPLETE_TAG_OPEN, '<div'],
[lex.TokenType.TEXT, '"'],
[lex.TokenType.TAG_OPEN_START, '<span'],
[lex.TokenType.TAG_OPEN_END, '>'],
[lex.TokenType.TAG_CLOSE, '</span>'],
[lex.TokenType.EOF, ''],
]);
});
});
});
describe('attributes', () => {
@ -554,7 +593,8 @@ import {ParseLocation, ParseSourceFile, ParseSourceSpan} from '../../src/parse_u
expect(tokenizeAndHumanizeSourceSpans('<p>a<b</p>')).toEqual([
[lex.TokenType.TAG_OPEN_START, '<p'],
[lex.TokenType.TAG_OPEN_END, '>'],
[lex.TokenType.TEXT, 'a<b'],
[lex.TokenType.TEXT, 'a'],
[lex.TokenType.INCOMPLETE_TAG_OPEN, '<b'],
[lex.TokenType.TAG_CLOSE, '</p>'],
[lex.TokenType.EOF, ''],
]);
@ -579,25 +619,41 @@ import {ParseLocation, ParseSourceFile, ParseSourceSpan} from '../../src/parse_u
it('should parse start tags quotes in place of an attribute name as text', () => {
expect(tokenizeAndHumanizeParts('<t ">')).toEqual([
[lex.TokenType.TEXT, '<t ">'],
[lex.TokenType.INCOMPLETE_TAG_OPEN, '', 't'],
[lex.TokenType.TEXT, '">'],
[lex.TokenType.EOF],
]);
expect(tokenizeAndHumanizeParts('<t \'>')).toEqual([
[lex.TokenType.TEXT, '<t \'>'],
[lex.TokenType.INCOMPLETE_TAG_OPEN, '', 't'],
[lex.TokenType.TEXT, '\'>'],
[lex.TokenType.EOF],
]);
});
it('should parse start tags quotes in place of an attribute name (after a valid attribute) as text',
it('should parse start tags quotes in place of an attribute name (after a valid attribute)',
() => {
expect(tokenizeAndHumanizeParts('<t a="b" ">')).toEqual([
[lex.TokenType.TEXT, '<t a="b" ">'],
[lex.TokenType.INCOMPLETE_TAG_OPEN, '', 't'],
[lex.TokenType.ATTR_NAME, '', 'a'],
[lex.TokenType.ATTR_QUOTE, '"'],
[lex.TokenType.ATTR_VALUE, 'b'],
[lex.TokenType.ATTR_QUOTE, '"'],
// TODO(ayazhafiz): the " symbol should be a synthetic attribute,
// allowing us to complete the opening tag correctly.
[lex.TokenType.TEXT, '">'],
[lex.TokenType.EOF],
]);
expect(tokenizeAndHumanizeParts('<t a=\'b\' \'>')).toEqual([
[lex.TokenType.TEXT, '<t a=\'b\' \'>'],
[lex.TokenType.INCOMPLETE_TAG_OPEN, '', 't'],
[lex.TokenType.ATTR_NAME, '', 'a'],
[lex.TokenType.ATTR_QUOTE, '\''],
[lex.TokenType.ATTR_VALUE, 'b'],
[lex.TokenType.ATTR_QUOTE, '\''],
// TODO(ayazhafiz): the ' symbol should be a synthetic attribute,
// allowing us to complete the opening tag correctly.
[lex.TokenType.TEXT, '\'>'],
[lex.TokenType.EOF],
]);
});