Improve error messages to show problematic position in the filter

This commit improves the parser and compiler error messages, making
it more easier to understand where in the filter the problem is.
Like modern compilers, jq will show the line in the filter where the
error occurred, will display squiggly line under the invalid token.

Author: itchyny

src/jq_test.c

@@ -70,8 +70,6 @@ static void test_err_cb(void *data, jv e) {
     e = jv_dump_string(e, JV_PRINT_INVALID);
   if (!strncmp(jv_string_value(e), "jq: error", sizeof("jq: error") - 1))
     snprintf(err_data->buf, sizeof(err_data->buf), "%s", jv_string_value(e));
-  if (strchr(err_data->buf, '\n'))
-    *(strchr(err_data->buf, '\n')) = '\0';
   jv_free(e);
 }
 
@@ -108,18 +106,7 @@ static void run_jq_tests(jv lib_dirs, int verbose, FILE *testdata, int skip, int
 
     if (skip > 0) {
       skip--;
-
-      // skip past test data
-      while (fgets(buf, sizeof(buf), testdata)) {
-        lineno++;
-        if (buf[0] == '\n' || (buf[0] == '\r' && buf[1] == '\n'))
-          break;
-      }
-
-      must_fail = 0;
-      check_msg = 0;
-
-      continue;
+      goto next;
     } else if (skip == 0) {
       printf("Skipped %d tests\n", tests_to_skip);
       skip = -1;
@@ -139,37 +126,40 @@ static void run_jq_tests(jv lib_dirs, int verbose, FILE *testdata, int skip, int
 
     if (must_fail) {
       jq_set_error_cb(jq, NULL, NULL);
-      if (!fgets(buf, sizeof(buf), testdata)) { invalid++; break; }
-      lineno++;
-      if (buf[strlen(buf)-1] == '\n') buf[strlen(buf)-1] = 0;
       if (compiled) {
-        printf("*** Test program compiled that should not have at line %u: %s\n", lineno, prog);
-        must_fail = 0;
-        check_msg = 0;
-        invalid++;
-        continue;
+        printf("*** Test program compiled successfully, but should fail at line number %u: %s\n", lineno, prog);
+        goto fail;
+      }
+      char *err_buf = err_msg.buf;
+      while (fgets(buf, sizeof(buf), testdata)) {
+        lineno++;
+        if (skipline(buf)) break;
+        if (check_msg) {
+          if (buf[strlen(buf)-1] == '\n') buf[strlen(buf)-1] = '\0';
+          if (strncmp(buf, err_buf, strlen(buf)) != 0) {
+            if (strchr(err_buf, '\n')) *strchr(err_buf, '\n') = '\0';
+            printf("*** Erroneous program failed with '%s', but expected '%s' at line number %u: %s\n", err_buf, buf, lineno, prog);
+            goto fail;
+          }
+          err_buf += strlen(buf);
+          if (*err_buf == '\n') err_buf++;
+        }
       }
-      if (check_msg && strcmp(buf, err_msg.buf) != 0) {
-        printf("*** Erroneous test program failed with wrong message (%s) at line %u: %s\n", err_msg.buf, lineno, prog);
+      if (check_msg && *err_buf != '\0') {
+        if (strchr(err_buf, '\n')) *strchr(err_buf, '\n') = '\0';
+        printf("*** Erroneous program failed with extra message '%s' at line %u: %s\n", err_buf, lineno, prog);
         invalid++;
-      } else {
-        passed++;
+        pass = 0;
       }
       must_fail = 0;
       check_msg = 0;
+      passed += pass;
       continue;
     }
 
     if (!compiled) {
       printf("*** Test program failed to compile at line %u: %s\n", lineno, prog);
-      invalid++;
-      // skip past test data
-      while (fgets(buf, sizeof(buf), testdata)) {
-        lineno++;
-        if (buf[0] == '\n' || (buf[0] == '\r' && buf[1] == '\n'))
-          break;
-      }
-      continue;
+      goto fail;
     }
     if (verbose) {
       printf("Disassembly:\n");
@@ -181,8 +171,7 @@ static void run_jq_tests(jv lib_dirs, int verbose, FILE *testdata, int skip, int
     jv input = jv_parse(buf);
     if (!jv_is_valid(input)) {
       printf("*** Input is invalid on line %u: %s\n", lineno, buf);
-      invalid++;
-      continue;
+      goto fail;
     }
     jq_start(jq, input, verbose ? JQ_DEBUG_TRACE : 0);
 
@@ -192,8 +181,7 @@ static void run_jq_tests(jv lib_dirs, int verbose, FILE *testdata, int skip, int
       jv expected = jv_parse(buf);
       if (!jv_is_valid(expected)) {
         printf("*** Expected result is invalid on line %u: %s\n", lineno, buf);
-        invalid++;
-        continue;
+        goto fail;
       }
       jv actual = jq_next(jq);
       if (!jv_is_valid(actual)) {
@@ -226,12 +214,25 @@ static void run_jq_tests(jv lib_dirs, int verbose, FILE *testdata, int skip, int
         printf("*** Superfluous result: ");
         jv_dump(extra, 0);
         printf(" for test at line number %u, %s\n", lineno, prog);
+        invalid++;
         pass = 0;
       } else {
         jv_free(extra);
       }
     }
-    passed+=pass;
+    passed += pass;
+    continue;
+
+fail:
+    invalid++;
+
+next:
+    while (fgets(buf, sizeof(buf), testdata)) {
+      lineno++;
+      if (skipline(buf)) break;
+    }
+    must_fail = 0;
+    check_msg = 0;
   }
   jq_teardown(&jq);
 

src/locfile.c

@@ -7,7 +7,7 @@
 #include "jq.h"
 #include "jv_alloc.h"
 #include "locfile.h"
-
+#include "util.h"
 
 struct locfile* locfile_init(jq_state *jq, const char *fname, const char* data, int length) {
   struct locfile* l = jv_mem_alloc(sizeof(struct locfile));
@@ -63,13 +63,6 @@ static int locfile_line_length(struct locfile* l, int line) {
 void locfile_locate(struct locfile* l, location loc, const char* fmt, ...) {
   va_list fmtargs;
   va_start(fmtargs, fmt);
-  int startline;
-  int offset;
-
-  if (loc.start != -1) {
-    startline = locfile_get_line(l, loc.start);
-    offset = l->linemap[startline];
-  }
 
   jv m1 = jv_string_vfmt(fmt, fmtargs);
   va_end(fmtargs);
@@ -78,16 +71,23 @@ void locfile_locate(struct locfile* l, location loc, const char* fmt, ...) {
     return;
   }
   if (loc.start == -1) {
-    jq_report_error(l->jq, jv_string_fmt("jq: error: %s\n<unknown location>", jv_string_value(m1)));
+    jq_report_error(l->jq, jv_string_fmt("jq: error: %s", jv_string_value(m1)));
     jv_free(m1);
     return;
   }
-  jv m2 = jv_string_fmt("%s at %s, line %d, column %d:\n%.*s%*s",
+
+  int startline = locfile_get_line(l, loc.start);
+  int offset = l->linemap[startline];
+  int end = MIN(loc.end, l->linemap[startline+1] - 1);
+  assert(end > loc.start);
+  jv underline = jv_string_repeat(jv_string("^"), end - loc.start);
+  jv m2 = jv_string_fmt("%s at %s, line %d, column %d:\n    %.*s\n    %*s",
                         jv_string_value(m1), jv_string_value(l->fname),
                         startline + 1, loc.start - offset + 1,
                         locfile_line_length(l, startline), l->data + offset,
-                        loc.start - offset, "");
+                        end - offset, jv_string_value(underline));
   jv_free(m1);
+  jv_free(underline);
   jq_report_error(l->jq, m2);
   return;
 }