Add p_parse_inner_XXX() APIs

spec/test_parse_inner_shared.c

@@ -0,0 +1,83 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+#include "testutils.h"
+
+int main()
+{
+    /* Grammar:
+     *   start Start;
+     *   start R1;
+     *   Start -> R1 a;
+     *   Start -> R2 b;
+     *   R1 -> a b   << $$ = 11; >>
+     *   R2 -> a b   << $$ = 22; >>
+     *   token a; token b;
+     *
+     * The rules `R1 -> a b` and `R2 -> a b` produce identical input. Within
+     * parse_Start, the generated parser differentiates the reduce by
+     * lookahead: `a` selects R1 (because `Start -> R1 a`) and `b` selects R2
+     * (because `Start -> R2 b`). Within parse_R1, the reduce is unconditional
+     * on any lookahead. This test exercises p_parse_inner_R1() to confirm
+     * that reductions to R1 succeed even when the incoming follow token is
+     * not the natural lookahead used by parse_Start's disambiguation. */
+
+    /* Sanity-check that parse_Start resolves R1 vs R2 via lookahead in the
+     * shared "a b" state. */
+    char const * input = "aba";
+    p_context_t * context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse_Start(context) == P_SUCCESS);
+    p_context_delete(context);
+
+    input = "abb";
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse_Start(context) == P_SUCCESS);
+    p_context_delete(context);
+
+    /* Standard parse of R1 succeeds on "ab". */
+    input = "ab";
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse_R1(context) == P_SUCCESS);
+    assert_eq(11u, (size_t)p_result_R1(context));
+    p_context_delete(context);
+
+    /* Standard parse of R1 fails on "abb" (unexpected trailing token). */
+    input = "abb";
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse_R1(context) == P_UNEXPECTED_TOKEN);
+    p_context_delete(context);
+
+    /* parse_inner_R1("abb", [b]) succeeds: even though `b` is the lookahead
+     * that parse_Start uses to select R2 over R1 in the ambiguous state, from
+     * R1's start state the reduce to R1 is unconditional, and the follow-
+     * token shift retry at the R1-accepting state completes the parse. */
+    {
+        input = "abb";
+        context = p_context_new((uint8_t const *)input, strlen(input));
+        p_token_t follow_tokens[] = { TOKEN_b };
+        assert(p_parse_inner_R1(context, follow_tokens, 1u) == P_SUCCESS);
+        assert_eq(11u, (size_t)p_result_R1(context));
+        p_context_delete(context);
+    }
+
+    /* parse_inner_R1("aba", [a]) also succeeds: `a` is the follow token
+     * parse_Start uses to select R1, and it works here as a follow token
+     * too. */
+    {
+        input = "aba";
+        context = p_context_new((uint8_t const *)input, strlen(input));
+        p_token_t follow_tokens[] = { TOKEN_a };
+        assert(p_parse_inner_R1(context, follow_tokens, 1u) == P_SUCCESS);
+        assert_eq(11u, (size_t)p_result_R1(context));
+        p_context_delete(context);
+    }
+
+    /* parse_inner_R1("ab", NULL) behaves like p_parse_R1("ab"). */
+    input = "ab";
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse_inner_R1(context, NULL, 0u) == P_SUCCESS);
+    assert_eq(11u, (size_t)p_result_R1(context));
+    p_context_delete(context);
+
+    return 0;
+}