indent fix

src/indent_helper.hpp

@@ -13,17 +13,17 @@ public:
     {
         int current = indent_stack.top();
 
+        if (spaces == current)
+        {
+            return 0;
+        }
+
         if (spaces > current)
         {
             indent_stack.push(spaces);
             return 1;
         }
 
-        if (spaces == current)
-        {
-            return 0;
-        }
-
         pending_dedents = 0;
         while (indent_stack.top() > spaces)
         {
@@ -31,35 +31,23 @@ public:
             pending_dedents++;
         }
 
-        if (indent_stack.top() != spaces)
-        {
-            throw std::runtime_error("Indentation error");
-        }
-
-        return -1;
-    }
-
-    bool hasPendingDedents() const
-    {
-        return pending_dedents > 0;
-    }
-
-    void consumePendingDedent()
-    {
         if (pending_dedents > 0)
         {
             pending_dedents--;
-        }
+            return -1;
         }
 
-    int flushAllDedents()
-    {
-        int total_dedents = 0;
-        while (indent_stack.size() > 1)
-        {
-            indent_stack.pop();
-            total_dedents++;
+        return 0;
     }
-        return total_dedents;
+
+    // returns false on failure
+    bool consumeDedent()
+    {
+        if (pending_dedents <= 0)
+        {
+            return false;
+        }
+        pending_dedents--;
+        return true;
     }
 };

src/lexer.l

@@ -7,18 +7,13 @@
 #include "scanner.hpp"
 #include "indent_helper.hpp"
 
-IndentHelper indent_helper;
-bool at_line_start = true;
 %}
 
 %%
+^[ \t]*\r?\n   { /* Ignore lines containing whitespace only */ }
+^[ \t]*#.*\n   { /* Ignore comment-only lines */ }
 
 ^[ \t]* {
-    if (!at_line_start) {
-        REJECT;
-    }
-    at_line_start = false;
-
     int spaces = 0;
     for (int i = 0; i < yyleng; i++)
         spaces += (yytext[i] == '\t') ? 8 : 1;
@@ -28,10 +23,7 @@ bool at_line_start = true;
     if (result < 0) return yy::parser::token::TOK_DEDENT;
 }
 
-\n {
-    at_line_start = true;
-    return yy::parser::token::TOK_NEWLINE;
-}
+\n       { return yy::parser::token::TOK_NEWLINE; }
 
 def      { return yy::parser::token::TOK_KW_DEF; }
 if       { return yy::parser::token::TOK_KW_IF; }
@@ -54,15 +46,5 @@ in       { return yy::parser::token::TOK_KW_IN; }
 [0-9]+      { yylval->as<std::string>() = yytext; return yy::parser::token::TOK_NUMBER; }
 [A-Za-z_][A-Za-z0-9_]*  { yylval->as<std::string>() = yytext; return yy::parser::token::TOK_IDENTIFIER; }
 
-
-<<EOF>> {
-    if (indent_helper.hasPendingDedents()) {
-        indent_helper.consumeDedent();
-        return yy::parser::token::TOK_DEDENT;
-    }
-    int d;
-    if ((d = indent_helper.flushDedent()) != 0) return yy::parser::token::TOK_DEDENT;
-    return yy::parser::token::TOK_EOF;
-}
-
+<<EOF>>  { return yy::parser::token::TOK_EOF; }
 .           { /* ignore other characters */ }

src/scanner.hpp

@@ -5,21 +5,38 @@
 #endif
 
 #include "parser.hpp"
+#include "indent_helper.hpp"
 #include <string>
 
 class Scanner : public yyFlexLexer
 {
 public:
+    IndentHelper indent_helper;
     Scanner(std::istream &in) : yyFlexLexer(&in), yylval(nullptr) {}
 
     int lex(yy::parser::semantic_type *lval)
     {
+        if (indent_helper.consumeDedent())
+        {
+            return yy::parser::token::TOK_DEDENT;
+        }
         this->yylval = lval;
-        return yylex();
+        int token = yylex();
+
+        if (token == yy::parser::token::TOK_EOF)
+        {
+            int result = indent_helper.processLine(0);
+
+            if (result == -1)
+            {
+                return yy::parser::token::TOK_DEDENT;
+            }
+        }
+
+        return token;
     }
 
 private:
-    // implemented by flex
     virtual int yylex() override;
     yy::parser::semantic_type *yylval;
 };