Add halt, halt_error builtins (fix #386)

src/builtin.c

@@ -1031,6 +1031,19 @@ static jv f_env(jq_state *jq, jv input) {
   return env;
 }
 
+static jv f_halt(jq_state *jq, jv input) {
+  jv_free(input);
+  jq_halt(jq, jv_invalid(), jv_invalid());
+  return jv_true();
+}
+
+static jv f_halt_error(jq_state *jq, jv input, jv a) {
+  if (jv_get_kind(a) != JV_KIND_NUMBER)
+    return type_error(input, "halt_error/1: number required"); \
+  jq_halt(jq, a, input);
+  return jv_true();
+}
+
 static jv f_get_search_list(jq_state *jq, jv input) {
   jv_free(input);
   return jq_get_lib_dirs(jq);
@@ -1467,6 +1480,8 @@ static const struct cfunction function_list[] = {
   {(cfunction_ptr)f_error, "error", 2},
   {(cfunction_ptr)f_format, "format", 2},
   {(cfunction_ptr)f_env, "env", 1},
+  {(cfunction_ptr)f_halt, "halt", 1},
+  {(cfunction_ptr)f_halt_error, "halt_error", 2},
   {(cfunction_ptr)f_get_search_list, "get_search_list", 1},
   {(cfunction_ptr)f_get_prog_origin, "get_prog_origin", 1},
   {(cfunction_ptr)f_get_jq_origin, "get_jq_origin", 1},

src/builtin.jq

@@ -1,3 +1,4 @@
+def halt_error: halt_error(5);
 def error: error(.);
 def map(f): [.[] | f];
 def select(f): if f then . else empty end;

src/execute.c

@@ -40,6 +40,10 @@ struct jq_state {
   int initial_execution;
   unsigned next_label;
 
+  int halted;
+  jv exit_code;
+  jv error_message;
+
   jv attrs;
   jq_input_cb input_cb;
   void *input_cb_data;
@@ -285,6 +289,9 @@ static void jq_reset(jq_state *jq) {
   jv_free(jq->error);
   jq->error = jv_null();
 
+  jq->halted = 0;
+  jv_free(jq->exit_code);
+  jv_free(jq->error_message);
   if (jv_get_kind(jq->path) != JV_KIND_INVALID)
     jv_free(jq->path);
   jq->path = jv_null();
@@ -320,6 +327,11 @@ jv jq_next(jq_state *jq) {
   jq->initial_execution = 0;
   assert(jv_get_kind(jq->error) == JV_KIND_NULL);
   while (1) {
+    if (jq->halted) {
+      if (jq->debug_trace_enabled)
+        printf("\t<halted>\n");
+      return jv_invalid();
+    }
     uint16_t opcode = *pc;
     raising = 0;
 
@@ -932,6 +944,10 @@ jq_state *jq_init(void) {
   jq->curr_frame = 0;
   jq->error = jv_null();
 
+  jq->halted = 0;
+  jq->exit_code = jv_invalid();
+  jq->error_message = jv_invalid();
+
   jq->err_cb = default_err_cb;
   jq->err_cb_data = stderr;
 
@@ -1163,3 +1179,28 @@ void jq_get_debug_cb(jq_state *jq, jq_msg_cb *cb, void **data) {
   *cb = jq->debug_cb;
   *data = jq->debug_cb_data;
 }
+
+void
+jq_halt(jq_state *jq, jv exit_code, jv error_message)
+{
+  assert(!jq->halted);
+  jq->halted = 1;
+  jq->exit_code = exit_code;
+  jq->error_message = error_message;
+}
+
+int
+jq_halted(jq_state *jq)
+{
+  return jq->halted;
+}
+
+jv jq_get_exit_code(jq_state *jq)
+{
+  return jv_copy(jq->exit_code);
+}
+
+jv jq_get_error_message(jq_state *jq)
+{
+  return jv_copy(jq->error_message);
+}

src/jq.h

@@ -22,6 +22,11 @@ void jq_start(jq_state *, jv value, int);
 jv jq_next(jq_state *);
 void jq_teardown(jq_state **);
 
+void jq_halt(jq_state *, jv, jv);
+int jq_halted(jq_state *);
+jv jq_get_exit_code(jq_state *);
+jv jq_get_error_message(jq_state *);
+
 typedef jv (*jq_input_cb)(jq_state *, void *);
 void jq_set_input_cb(jq_state *, jq_input_cb, void *);
 void jq_get_input_cb(jq_state *, jq_input_cb *, void **);

src/main.c

@@ -137,10 +137,11 @@ enum {
   RAW_NO_LF             = 1024,
   UNBUFFERED_OUTPUT     = 2048,
   EXIT_STATUS           = 4096,
-  SEQ                   = 8192,
-  RUN_TESTS             = 16384,
+  EXIT_STATUS_EXACT     = 8192,
+  SEQ                   = 16384,
+  RUN_TESTS             = 32768,
   /* debugging only */
-  DUMP_DISASM           = 32768,
+  DUMP_DISASM           = 65536,
 };
 static int options = 0;
 
@@ -182,7 +183,29 @@ static int process(jq_state *jq, jv value, int flags, int dumpopts) {
     if (options & UNBUFFERED_OUTPUT)
       fflush(stdout);
   }
-  if (jv_invalid_has_msg(jv_copy(result))) {
+  if (jq_halted(jq)) {
+    // jq program invoked `halt` or `halt_error`
+    options |= EXIT_STATUS_EXACT;
+    jv exit_code = jq_get_exit_code(jq);
+    if (!jv_is_valid(exit_code))
+      ret = 0;
+    else if (jv_get_kind(exit_code) == JV_KIND_NUMBER)
+      ret = jv_number_value(exit_code);
+    else
+      ret = 5;
+    jv_free(exit_code);
+    jv error_message = jq_get_error_message(jq);
+    if (jv_get_kind(error_message) == JV_KIND_STRING) {
+      fprintf(stderr, "%s", jv_string_value(error_message));
+    } else if (jv_get_kind(error_message) == JV_KIND_NULL) {
+      // Halt with no output
+    } else if (jv_is_valid(error_message)) {
+      error_message = jv_dump_string(jv_copy(error_message), 0);
+      fprintf(stderr, "%s\n", jv_string_value(error_message));
+    } // else no message on stderr; use --debug-trace to see a message
+    fflush(stderr);
+    jv_free(error_message);
+  } else if (jv_invalid_has_msg(jv_copy(result))) {
     // Uncaught jq exception
     jv msg = jv_invalid_get_msg(jv_copy(result));
     jv input_pos = jq_util_input_get_position(jq);
@@ -623,7 +646,7 @@ out:
   jq_teardown(&jq);
   if (ret >= 10 && (options & EXIT_STATUS))
     return ret - 10;
-  if (ret >= 10)
+  if (ret >= 10 && !(options & EXIT_STATUS_EXACT))
     return 0;
   return ret;
 }