Indent the line after a `=>' left at the end of a line

An arrow function whose body starts on the next line fell back to
column zero:

    $f = fn($x) =>
    $x + 1;

`=>' is deliberately excluded from php-indent--indent-operator-re --- in
PHP it is overwhelmingly the array key operator, and treating every
`'key' => 'value'' as a continuation would be wrong --- so nothing at
all picked up a trailing one, and the body was indented as if it began
a fresh statement.

Property hooks showed the same gap, and worse, an inconsistent one: the
first line after `get =>' stayed put while a following `.' line was
indented by php-indent--statement-continuation-indentation, which does
fire after an identifier:

    get =>
    $this->a
        . ' ';

Treat a trailing `=>' as leaving the statement open, alongside the
identifier / `)' / `):' cases already there.  The three shapes now
agree:

    $f = fn($x) =>
        $x + 1;

    $config = [
        'key' =>
            'a value long enough to wrap',
    ];

    get =>
        $this->a
        . ' ';

Only `=>' is matched, so `>=', `->' and `<=>' keep the handling they
had.  The shape had no fixture at all, which is why the gap went
unnoticed; tests/indent/trailing-arrow.php now covers arrow functions,
array values, the bracket-on-the-same-line case, property hooks, match
arms, and a `>=' left at the end of a line.

Author: zonuexe

lisp/php-indent.el

@@ -464,9 +464,10 @@ until a statement terminator (`;', `{', `}', an opening `(' or `[', a
 A continuation line is one whose previous code token leaves the
 statement unterminated: an identifier or keyword (as in stacked member
 modifiers, `extends' on its own line or a broken `return'), a closing
-parenthesis, or a return-type `):'.  Such lines are indented one
-`php-indent-offset' beyond the first line of the statement.  Return nil
-when the current line does not continue a statement this way."
+parenthesis, a return-type `):', or a trailing `=>'.  Such lines are
+indented one `php-indent-offset' beyond the first line of the
+statement.  Return nil when the current line does not continue a
+statement this way."
   (save-excursion
     (back-to-indentation)
     (unless (or (memq (char-after) '(?\{ ?\} ?\) ?\]))
@@ -480,7 +481,15 @@ when the current line does not continue a statement this way."
                        ;; A `):' return-type (or alternative-syntax `):')
                        ;; also leaves the statement open.
                        (and (eq (char-before) ?:)
-                            (eq (char-before (1- (point))) ?\)))))
+                            (eq (char-before (1- (point))) ?\)))
+                       ;; So does a `=>' left dangling at the end of a
+                       ;; line: an arrow function's body, an array value
+                       ;; or a property hook's expression follows it.
+                       ;; `=>' is excluded from
+                       ;; `php-indent--indent-operator-re', so nothing
+                       ;; else picks these up.
+                       (and (eq (char-before) ?>)
+                            (eq (char-before (1- (point))) ?=))))
           (goto-char pos)
           (php-indent--goto-statement-start)
           (unless (php-indent--same-line pos)

tests/indent/trailing-arrow.php

@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * A `=>' left dangling at the end of a line.
+ *
+ * `=>' is excluded from `php-indent--indent-operator-re' because it is
+ * PHP's array key operator, so nothing treated the line after it as a
+ * continuation: an arrow function's body fell all the way back to
+ * column zero.
+ */
+
+// An arrow function's body on the next line.
+$f = fn($x) =>
+    $x + 1;                                          // ###php-mode-test### ((indent 4))
+
+$g = static fn(int $n): bool =>
+    $n > 0;                                          // ###php-mode-test### ((indent 4))
+
+// An array value on the next line.
+$config = [
+    'key' =>                                         // ###php-mode-test### ((indent 4))
+        'a value long enough to wrap',               // ###php-mode-test### ((indent 8))
+    'other' => 1,                                    // ###php-mode-test### ((indent 4))
+];                                                   // ###php-mode-test### ((indent 0))
+
+// The opening bracket on the same line as the arrow: the value anchors
+// to the line holding the bracket, not to the key's column.
+$inline = ['key' =>
+    'value'];                                        // ###php-mode-test### ((indent 4))
+
+// A property hook's expression on the next line.
+class Person
+{
+    public string $label {                           // ###php-mode-test### ((indent 4))
+        get =>                                       // ###php-mode-test### ((indent 8))
+            $this->firstName                         // ###php-mode-test### ((indent 12))
+            . ' '                                    // ###php-mode-test### ((indent 12))
+            . $this->lastName;                       // ###php-mode-test### ((indent 12))
+    }                                                // ###php-mode-test### ((indent 4))
+}
+
+// A match arm's result on the next line.
+$label = match ($n) {
+    1 =>                                             // ###php-mode-test### ((indent 4))
+        'one',                                       // ###php-mode-test### ((indent 8))
+    default => 'many',                               // ###php-mode-test### ((indent 4))
+};                                                   // ###php-mode-test### ((indent 0))
+
+// Tokens that end in `>' but are not `=>' keep their own handling.
+if ($a >=
+    $b                                               // ###php-mode-test### ((indent 4))
+) {
+    echo 1;                                          // ###php-mode-test### ((indent 4))
+}

tests/php-mode-test.el

@@ -660,6 +660,14 @@ Meant for `php-mode-test-issue-503'."
   ;; Proper alignment arglist that contains empty lines.
   (with-php-mode-test ("indent/issue-793.php" :indent t :magic t)))
 
+(ert-deftest php-mode-test-indentation-trailing-arrow ()
+  "Indentation of a line following a `=>' left at the end of a line.
+
+`=>' is excluded from `php-indent--indent-operator-re' because it is
+PHP's array key operator, so nothing treated the next line as a
+continuation: an arrow function's body fell back to column zero."
+  (with-php-mode-test ("indent/trailing-arrow.php" :indent t :magic t)))
+
 (ert-deftest php-mode-test-indentation-object-accessor ()
   "Alignment of chained object accessors split across lines."
   (with-php-mode-test ("indent/issue-623.php" :indent t :magic t)))