fix ending heredoc identifiers must be on single line

README.md

@@ -37,4 +37,3 @@ The aim is to build unit testcases from selected failure classes and slowly get
     * [x] add quoted template interpolations
     * [ ] add quoted template directives
   * [x] add heredoc templates
-

example/real_world_stuff/coreos/coreos%tectonic-installer%modules%ignition%etcd.tf-155.hcl

@@ -12,14 +12,15 @@ After=coreos-metadata.service
 EOF
 
   cert_options = <<EOF
---cert-file=/etc/ssl/etcd/server.crt \
+  --cert-file=/etc/ssl/etcd/server.crt \
   --client-cert-auth=true \
   --key-file=/etc/ssl/etcd/server.key \
   --peer-cert-file=/etc/ssl/etcd/peer.crt \
   --peer-key-file=/etc/ssl/etcd/peer.key \
   --peer-trusted-ca-file=/etc/ssl/etcd/ca.crt \
   --peer-client-cert-auth=true \
-  --trusted-ca-file=/etc/ssl/etcd/ca.crtEOF
+  --trusted-ca-file=/etc/ssl/etcd/ca.crt
+EOF
 }
 
 data "template_file" "etcd_names" {

grammar.js

@@ -279,7 +279,6 @@ module.exports = grammar({
       $._quoted_template_end,
     )),
 
-    // TODO user chosen identifiers
     heredoc_template: $ => seq(
       $.heredoc_start,
       $.heredoc_identifier,

src/scanner.cc

@@ -73,7 +73,11 @@ public:
   }
 
   bool scan(TSLexer* lexer, const bool* valid_symbols) {
+    bool has_leading_whitespace_with_newline = false;
     while (iswspace(lexer->lookahead)) {
+      if (lexer->lookahead == '\n') {
+        has_leading_whitespace_with_newline = true;
+      }
       skip(lexer);
     }
     if (lexer->lookahead == '\0') {
@@ -127,7 +131,7 @@ public:
       context_stack.push_back({ .type = HEREDOC_TEMPLATE, .heredoc_identifier = identifier });
       return accept_and_advance(lexer, HEREDOC_IDENTIFIER);
     }
-    if (valid_symbols[HEREDOC_IDENTIFIER] && in_heredoc_context()) {
+    if (valid_symbols[HEREDOC_IDENTIFIER] && in_heredoc_context() && has_leading_whitespace_with_newline) {
       string expected_identifier = context_stack.back().heredoc_identifier;
 
       for (string::iterator it = expected_identifier.begin(); it != expected_identifier.end(); ++it) {

test/corpus/templates.txt

@@ -146,3 +146,26 @@ foo = "hello $${ world"
         (literal_value
           (string_lit
             (template_literal)))))))
+
+================================================================================
+tricky heredoc
+================================================================================
+
+foo = <<END
+    contains fake endings
+    END (ineligible) END
+END
+
+--------------------------------------------------------------------------------
+
+(config_file
+  (body
+    (attribute
+      (identifier)
+      (expression
+        (template_expr
+          (heredoc_template
+            (heredoc_start)
+            (heredoc_identifier)
+            (template_literal)
+            (heredoc_identifier)))))))