Syntax errors caused by unclosed {, [, ( mention specific location

Aside from a few very specific syntax errors for which detailed exceptions are
thrown, generally PHP just emits the default error messages generated by bison on syntax
error. These messages are very uninformative; they just say "Unexpected ... at line ...".

This is most problematic with constructs which can span an arbitrary number of lines, such
as blocks of code delimited by { }, 'if' conditions delimited by ( ), and so on. If a closing
delimiter is missed, the block will run for the entire remainder of the source file (which
could be thousands of lines), and then at the end, a parse error will be thrown with the
dreaded words: "Unexpected end of file".

Therefore, track the positions of opening and closing delimiters and ensure that they match
up correctly. If any mismatch or missing delimiter is detected, immediately throw a parse
error which points the user to the offending line. This is best done in the *lexer* and not
in the parser.

Thanks to Nikita Popov and George Peter Banyard for suggesting improvements.

Fixes bug #79368.
Closes GH-5364.

1 files changed, 57 insertions, 0 deletions

diff --git a/tests/lang/syntax_errors.phpt b/tests/lang/syntax_errors.phpt
new file mode 100644
index 0000000000..1fecb035de
--- /dev/null
+++ b/tests/lang/syntax_errors.phpt
@@ -0,0 +1,57 @@
+--TEST--
+Detailed reporting on specific types of syntax errors
+--FILE--
+<?
+$badCode = [
+  "if(1 > 2",                   /* unclosed ( */
+  "[1, 2,",                     /* unclosed [ */
+  "if(1) { echo 'hello'; ",     /* unclosed { */
+  "(1 + 2));",                  /* too many ) */
+  "[1, 2]]",                    /* too many ] */
+  "if (1) {  }  }",             /* too many } */
+  "(1 + 2];",                   /* ] doesn't match ( */
+  "[1, 2)];",                   /* ) doesn't match [ */
+  "if(1) { echo 'a'; )}",       /* ) doesn't match { */
+  /* separately test cases where the faulty construct spans multiple lines,
+     since the error message should refer to the starting line in those cases */
+  "if(1 > 2) {\n  echo '1';",   /* unclosed (, spans multiple lines */
+  "[1,\n2,\n3,",                /* unclosed [, spans multiple lines */
+  "{\n  echo '1';\n echo '2';", /* unclosed {, spans multiple lines */
+  "(1 +\n 2 +\n 3))",           /* too many ), spans multiple lines */
+  "[1,\n2,\n3]];",              /* too many ], spans multiple lines */
+  "if (1)\n  {\n    }}",        /* too many }, spans multiple lines */
+  "(1 +\n\n  2])",              /* ] doesn't match (, spans multiple lines */
+  "[1,\n2,\n3)]",               /* ) doesn't match [, spans multiple lines */
+  "if(1) {\n  echo 'a';\n)}",   /* ) doesn't match {, spans multiple lines */
+  ];
+
+foreach ($badCode as $code) {
+  try {
+    eval($code);
+  } catch (ParseError $e) {
+    echo $e->getMessage(), "\n";
+  }
+}
+
+echo "==DONE==\n";
+?>
+--EXPECT--
+Unclosed '('
+Unclosed '['
+Unclosed '{'
+Unmatched ')'
+Unmatched ']'
+Unmatched '}'
+Unclosed '(' does not match ']'
+Unclosed '[' does not match ')'
+Unclosed '{' does not match ')'
+Unclosed '{' on line 1
+Unclosed '[' on line 1
+Unclosed '{' on line 1
+Unmatched ')'
+Unmatched ']'
+Unmatched '}'
+Unclosed '(' on line 1 does not match ']'
+Unclosed '[' on line 1 does not match ')'
+Unclosed '{' on line 1 does not match ')'
+==DONE==