fix(compiler): allow newlines in track and let expressions (#52137)

Fixes that the template parser didn't allow for newlines in the `track` and `let` expressions of `@for` blocks.

Fixes #52132.

PR Close #52137

packages/compiler/src/render3/r3_control_flow.ts

@@ -17,7 +17,7 @@ import * as t from './r3_ast';
 const FOR_LOOP_EXPRESSION_PATTERN = /^\s*([0-9A-Za-z_$]*)\s+of\s+(.*)/;
 
 /** Pattern for the tracking expression in a for loop block. */
-const FOR_LOOP_TRACK_PATTERN = /^track\s+(.*)/;
+const FOR_LOOP_TRACK_PATTERN = /^track\s+([\S\s]*)/;
 
 /** Pattern for the `as` expression in a conditional block. */
 const CONDITIONAL_ALIAS_PATTERN = /^as\s+(.*)/;
@@ -26,7 +26,7 @@ const CONDITIONAL_ALIAS_PATTERN = /^as\s+(.*)/;
 const ELSE_IF_PATTERN = /^else[^\S\r\n]+if/;
 
 /** Pattern used to identify a `let` parameter. */
-const FOR_LOOP_LET_PATTERN = /^let\s+(.*)/;
+const FOR_LOOP_LET_PATTERN = /^let\s+([\S\s]*)/;
 
 /** Names of variables that are allowed to be used in the `let` expression of a `for` loop. */
 const ALLOWED_FOR_LOOP_LET_VARIABLES =

packages/compiler/test/render3/r3_template_transform_spec.ts

@@ -1516,6 +1516,24 @@ describe('R3 template transform', () => {
       ]);
     });
 
+    it('should parse a for loop block with newlines in its let parameters', () => {
+      expectFromHtml(`
+        @for (item of items.foo.bar; track item.id; let\nidx = $index,\nf = $first,\nc = $count,\nl = $last,\nev = $even,\nod = $odd) {
+          {{ item }}
+        }
+      `).toEqual([
+        ['ForLoopBlock', 'items.foo.bar', 'item.id'],
+        ['Variable', 'item', '$implicit'],
+        ['Variable', 'idx', '$index'],
+        ['Variable', 'f', '$first'],
+        ['Variable', 'c', '$count'],
+        ['Variable', 'l', '$last'],
+        ['Variable', 'ev', '$even'],
+        ['Variable', 'od', '$odd'],
+        ['BoundText', ' {{ item }} '],
+      ]);
+    });
+
     it('should parse nested for loop blocks', () => {
       expectFromHtml(`
         @for (item of items.foo.bar; track item.id) {
@@ -1553,6 +1571,21 @@ describe('R3 template transform', () => {
       ]);
     });
 
+    it('should parse a for loop block with newlines in its expression', () => {
+      const expectedResult = [
+        ['ForLoopBlock', 'items.foo.bar', 'item.id + foo'],
+        ['Variable', 'item', '$implicit'],
+        ['BoundText', '{{ item }}'],
+      ];
+
+      expectFromHtml(`
+        @for (item\nof\nitems.foo.bar; track item.id +\nfoo) {{{ item }}}
+      `).toEqual(expectedResult);
+      expectFromHtml(`
+        @for ((item\nof\nitems.foo.bar); track (item.id +\nfoo)) {{{ item }}}
+      `).toEqual(expectedResult);
+    });
+
     describe('validations', () => {
       it('should report if for loop does not have an expression', () => {
         expect(() => parse(`@for {hello}`)).toThrowError(/@for loop does not have an expression/);