Allow {% if VALUE1 == VALUE2 %}, with two defines

I was surprised to see that blogc doesn't support testing for equality
between two defined values, it just supports comparison between a
variable and a constant string.  I want to be able to compare two
variables so I can build the same source with different "-D" argument on
the command line to produce different outputs.

This patch adds support for this pattern.  I changed the parser to
include the '"' at the beginning and end of a string, which allows the
renderer to determine if the user passed in a string or a variable name.
This is a bit hacky and causes some of the tests to fail -- these tests
look at the string values coming out of the parser.  I updated the tests
to match the new behavior.

2 files changed, 38 insertions, 7 deletions

diff --git a/src/renderer.c b/src/renderer.c
index c5b3e9f..167145d 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -215,8 +215,24 @@ blogc_render(b_slist_t *tmpl, b_slist_t *sources, b_trie_t *config, bool listing
                 }
                 evaluate = false;
                 if (stmt->op != 0) {
-                    if (defined != NULL && stmt->value2 != NULL) {
-                        cmp = strcmp(defined, stmt->value2);
+                    // Strings that start with a '"' are actually strings, the
+                    // others are meant to be looked up as a second variable
+                    // check.
+                    char *defined2 = NULL;
+                    if (stmt->value2[0] != '"') {
+                        defined2 =
+                            b_strdup(blogc_get_variable(stmt->value2,
+                                                        config,
+                                                        inside_block ? tmp_source
+                                                                     : NULL)
+                            );
+                    } else {
+                        defined2 = b_strndup(stmt->value2 + 1,
+                                             strlen(stmt->value2) - 2);
+                    }
+
+                    if (defined != NULL && defined2 != NULL) {
+                        cmp = strcmp(defined, defined2);
                         if (cmp != 0 && stmt->op & BLOGC_TEMPLATE_OP_NEQ)
                             evaluate = true;
                         else if (cmp == 0 && stmt->op & BLOGC_TEMPLATE_OP_EQ)
@@ -226,6 +242,8 @@ blogc_render(b_slist_t *tmpl, b_slist_t *sources, b_trie_t *config, bool listing
                         else if (cmp > 0 && stmt->op & BLOGC_TEMPLATE_OP_GT)
                             evaluate = true;
                     }
+
+                    free(defined2);
                 }
                 else {
                     if (if_not && defined == NULL)
diff --git a/src/template-parser.c b/src/template-parser.c
index fd01ac2..f6912df 100644
--- a/src/template-parser.c
+++ b/src/template-parser.c
@@ -30,7 +30,8 @@ typedef enum {
     TEMPLATE_BLOCK_IF_OPERATOR_START,
     TEMPLATE_BLOCK_IF_OPERATOR,
     TEMPLATE_BLOCK_IF_OPERAND_START,
-    TEMPLATE_BLOCK_IF_OPERAND,
+    TEMPLATE_BLOCK_IF_STRING_OPERAND,
+    TEMPLATE_BLOCK_IF_VARIABLE_OPERAND,
     TEMPLATE_BLOCK_END,
     TEMPLATE_VARIABLE_START,
     TEMPLATE_VARIABLE,
@@ -303,6 +304,11 @@ blogc_template_parse(const char *src, size_t src_len, blogc_error_t **err)
             case TEMPLATE_BLOCK_IF_OPERAND_START:
                 if (c == ' ')
                     break;
+                if ((c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_') {
+                    state = TEMPLATE_BLOCK_IF_VARIABLE_OPERAND;
+                    start2 = current;
+                    break;
+                }
                 if (c != '"') {
                     op_start = 0;
                     op_end = 0;
@@ -311,16 +317,23 @@ blogc_template_parse(const char *src, size_t src_len, blogc_error_t **err)
                         "Invalid 'if' operand. Must be double-quoted static string.");
                     break;
                 }
-                state = TEMPLATE_BLOCK_IF_OPERAND;
-                start2 = current + 1;
+                state = TEMPLATE_BLOCK_IF_STRING_OPERAND;
+                start2 = current;
                 break;
 
-            case TEMPLATE_BLOCK_IF_OPERAND:
+            case TEMPLATE_BLOCK_IF_STRING_OPERAND:
                 if (c != '"')
                     break;
                 if (c == '"' && src[current - 1] == '\\')
                     break;
                 state = TEMPLATE_BLOCK_END;
+                end2 = current + 1;
+                break;
+
+           case TEMPLATE_BLOCK_IF_VARIABLE_OPERAND:
+                if ((c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_')
+                    break;
+                state = TEMPLATE_BLOCK_END;
                 end2 = current;
                 break;
 
@@ -446,7 +459,7 @@ blogc_template_parse(const char *src, size_t src_len, blogc_error_t **err)
     }
 
     if (*err == NULL) {
-        if (state == TEMPLATE_BLOCK_IF_OPERAND)
+        if (state == TEMPLATE_BLOCK_IF_STRING_OPERAND)
             *err = blogc_error_parser(BLOGC_ERROR_TEMPLATE_PARSER, src, src_len,
                 start2 - 1, "Found an open double-quoted string.");
         else if (if_count != 0)