akbasic/tests/parser_expressions.c

/**
 * @file parser_expressions.c
 * @brief Tests the expression grammar via the leaf renderer.
 */

#include "harness.h"

/* Parse a line and assert the shape of the tree it produced. */
static void expect_tree(const char *line, const char *want)
{
    akbasic_ASTLeaf *leaf = NULL;
    char rendered[AKBASIC_MAX_STRING_LENGTH];
    akerr_ErrorContext *e = NULL;

    e = harness_parse(line, &leaf);
    if ( e != NULL ) {
	fprintf(stderr, "FAIL: \"%s\" did not parse: %s\n", line, e->message);
	akbasic_test_failures += 1;
	test_discard_error(e);
	return;
    }
    e = akbasic_leaf_to_string(leaf, rendered, sizeof(rendered));
    if ( e != NULL ) {
	test_discard_error(e);
	akbasic_test_failures += 1;
	return;
    }
    TEST_REQUIRE(strcmp(rendered, want) == 0,
		 "\"%s\": expected %s, got %s", line, want, rendered);
}

static void expect_parse_error(const char *line)
{
    akbasic_ASTLeaf *leaf = NULL;
    akerr_ErrorContext *e = NULL;

    e = harness_parse(line, &leaf);
    TEST_REQUIRE(e != NULL, "\"%s\" should not have parsed", line);
    if ( e != NULL ) {
	test_discard_error(e);
    }
}

int main(void)
{
    akbasic_ASTLeaf *leaf = NULL;

    TEST_REQUIRE_OK(harness_start(NULL));

    /*
     * An assignment renders with an empty operator: the reference's
     * operatorToStr() has a case for EQUAL but none for ASSIGNMENT, so it prints
     * "( A# ...)". Reproduced, so these expectations look odd on purpose.
     */

    /* Multiplication binds tighter than addition. */
    expect_tree("PRINT 1 + 2 * 3", "(PRINT)");
    expect_tree("A# = 1 + 2 * 3", "( A# (+ 1 (* 2 3)))");
    expect_tree("A# = 1 * 2 + 3", "( A# (+ (* 1 2) 3))");
    expect_tree("A# = 8 / 2 / 2", "( A# (/ (/ 8 2) 2))");

    /* Grouping overrides precedence. */
    expect_tree("A# = (1 + 2) * 3", "( A# (* (group (+ 1 2)) 3))");

    /* Unary minus and NOT. */
    expect_tree("A# = -5", "( A# (- 5))");
    expect_tree("A# = NOT 1", "( A# (NOT 1))");

    /* Comparisons sit below the arithmetic. */
    expect_tree("A# = 1 + 1 == 2", "( A# (= (+ 1 1) 2))");
    expect_tree("A# = 1 <> 2", "( A# (<> 1 2))");

    /* AND and OR sit below comparison. */
    expect_tree("A# = 1 == 1 AND 2 == 2", "( A# (AND (= 1 1) (= 2 2)))");

    /* Exponent. */
    expect_tree("A# = 2 ^ 3", "( A# (^ 2 3))");

    /*
     * Addition loops over its operator; subtraction returns after one. So
     * `1 + 2 + 3` folds left, while `1 - 2 - 3` parses only `1 - 2` and leaves
     * `- 3` in the token stream for the statement loop to pick up as a second
     * statement. That silently computes the wrong answer -- TODO.md section 12
     * item 12 -- and is pinned here so the fix is a deliberate change to this
     * assertion and not an accident.
     */
    expect_tree("A# = 1 + 2 + 3", "( A# (+ (+ 1 2) 3))");
    expect_tree("A# = 1 - 2 - 3", "( A# (- 1 2))");

    /* An array reference parses as an identifier carrying a subscript list. */
    TEST_REQUIRE_OK(harness_parse("A#(2) = 1", &leaf));
    TEST_REQUIRE(leaf != NULL && leaf->left != NULL, "assignment must have an lvalue");
    if ( leaf != NULL && leaf->left != NULL ) {
	TEST_REQUIRE_INT(leaf->left->leaftype, AKBASIC_LEAF_IDENTIFIER_INT);
	TEST_REQUIRE(akbasic_leaf_first_subscript(leaf->left) != NULL,
		     "A#(2) must carry an array subscript");
    }

    /* Failure paths. */
    expect_parse_error("A# = ");
    expect_parse_error("A# = (1 + 2");
    expect_parse_error("A# = *");

    harness_stop();
    return akbasic_test_failures;
}