Avoid duplication of error messages (#758)

# Description
* Improved error handling logics

## Type of change
- [x] Bug fix & code cleanup
- [ ] New feature
- [ ] Documentation update
- [ ] Test update

## Checklist for the reviewer
This checklist should be used as a help for the reviewer.

- [ ] Is the change limited to one issue?
- [ ] Does this PR close the issue?
- [ ] Is the code easy to read and understand?
- [ ] Do all new feature have an accompanying new test?
- [ ] Has the documentation been updated as necessary?

.github/workflows/cd_docs.yml

@@ -43,6 +43,8 @@ jobs:
         run: |
           sudo apt-get update --fix-missing
           sudo apt-get install \
+            libxml2-dev \
+            libxslt-dev \
             libhdf5-dev \
             swig4.0 \
             doxygen \

.github/workflows/ci_tests.yml

@@ -14,6 +14,8 @@ jobs:
       run: |
         sudo apt-get update --fix-missing && \
         sudo apt-get install \
+          libxml2-dev \
+          libxslt-dev \
           libhdf5-dev \
           swig4.0 \
           doxygen \

src/utils/err.c

@@ -195,7 +195,6 @@ int _err_vformat(ErrLevel errlevel, int eval, int errnum, const char *file,
   int ignore_new_error = 0;
   ErrHandler handler = err_get_handler();
   ErrNameConv nameconv = err_get_nameconv();
-  int call_handler = handler && !tls->err_record->prev;
 
   /* Check warning mode */
   if (errlevel == errLevelWarn) {
@@ -218,6 +217,7 @@ int _err_vformat(ErrLevel errlevel, int eval, int errnum, const char *file,
     switch (override) {
     case errOverrideAppend:
       n = strlen(errmsg);
+      tls->err_record->pos = n;
       n += snprintf(errmsg + n, errsize - n, "%s", err_append_sep);
       break;
     case errOverrideWarnOld:
@@ -283,25 +283,25 @@ int _err_vformat(ErrLevel errlevel, int eval, int errnum, const char *file,
     tls->err_record->reraise = eval;
 
   /* If we are not within a ErrTry...ErrEnd clause */
-  if (call_handler) {
+  if (!tls->err_record->prev) {
 
     /* ...call the error handler */
-    handler(tls->err_record);
+    if (handler) handler(tls->err_record);
 
     /* ...check err_abort_mode */
     if (errlevel >= errLevelError) {
       if (abort_mode == errAbortExit) {
-        if (!call_handler) handler(tls->err_record);
+        if (!handler) err_default_handler(tls->err_record);
         exit(eval);
       } else if (abort_mode >= errAbortAbort) {
-        if (!call_handler) handler(tls->err_record);
+        if (!handler) err_default_handler(tls->err_record);
         abort();
       }
     }
 
     /* ...make sure that fatal errors always exit */
     if (errlevel >= errLevelFatal) {
-      if (!call_handler) handler(tls->err_record);
+      if (!handler) err_default_handler(tls->err_record);
       exit(eval);
     }
   }
@@ -449,6 +449,7 @@ void err_clear(void)
   tls->err_record->eval = 0;
   tls->err_record->errnum = 0;
   tls->err_record->msg[0] = '\0';
+  tls->err_record->pos = 0;
   tls->err_record->handled = 0;
   tls->err_record->reraise = 0;
   tls->err_record->state = 0;
@@ -673,15 +674,42 @@ int err_get_color_coded()
 void err_default_handler(const ErrRecord *record)
 {
   FILE *stream = err_get_stream();
-  if (err_get_color_coded()) {
-    //if ((stream == stderr || stream == stdout) && getenv("ERR_COLOR")) {
-    /* Output the first word of the error message in red and the remaining
-       of it in magenta. */
-    int n = strcspn(record->msg, ": ");
-    fprintf(stream, "\033[31m%.*s\033[35m%s\033[0m\n", n, record->msg,
-            record->msg+n);
+  const char *msg = record->msg + record->pos;
+  char *errmark = (record->pos) ? "" : "** ";
+  if (record->pos >= ERR_MSGSIZE) return;
+  if (record->pos) {
+    int m = strspn(msg, "\n");
+    int n = strlen(err_append_sep) - m;
+    fprintf(stream, "%.*s", n, msg+m);
+    msg += m+n;
+  }
+  if (stream && err_get_color_coded()) {
+    /* Print error message in colour. */
+    int n;
+    ThreadLocals *tls = get_tls();
+    Globals *g = tls->globals;
+    ErrDebugMode debug_mode = err_get_debug_mode();
+    if (g->err_prefix && *g->err_prefix) {
+      n = strlen(g->err_prefix) + 2;
+      if (!record->pos) fprintf(stream, "\033[02;31m%.*s", n, msg);
+      msg += n;
+    }
+    if (debug_mode >= 1) {
+      n = strcspn(msg, ":") + 1;
+      n += (msg[0] == '(') ? 1 : strcspn(msg+n, ":") + 2;
+      fprintf(stream, "\033[00;34m%.*s", n, msg);
+      msg += n;
+    }
+    if (debug_mode >= 2) {
+      n = strcspn(msg, ":") + 2;
+      fprintf(stream, "\033[02;32m%.*s", n, msg);
+      msg += n;
+    }
+    n = strcspn(msg, ": ");
+    fprintf(stream, "\033[00;31m%.*s\033[02;35m%s\033[0m\n", n, msg, msg+n);
   } else if (stream) {
-    fprintf(stream, "** %s\n", record->msg);
+    /* Print error message with error marker prepended. */
+    fprintf(stream, "%s%s\n", errmark, msg);
   }
 }
 
@@ -756,7 +784,6 @@ void _err_link_record(ErrRecord *record)
 void _err_unlink_record(ErrRecord *record)
 {
   ThreadLocals *tls = get_tls();
-  Globals *g = tls->globals;
   assert(record == tls->err_record);
   assert(tls->err_record->prev);
 
@@ -800,7 +827,7 @@ void _err_unlink_record(ErrRecord *record)
 
     if (!tls->err_record->prev) {
       ErrHandler handler = err_get_handler();
-      if (handler) g->err_handler(tls->err_record);
+      if (handler) handler(tls->err_record);
     }
 
     if ((abort_mode && record->level >= errLevelError) ||

src/utils/err.h

@@ -504,6 +504,7 @@ typedef struct ErrRecord {
   int eval;               /*!< @brief Error value. */
   int errnum;             /*!< @brief System error number. */
   char msg[ERR_MSGSIZE];  /*!< @brief Error message. */
+  int pos;                /*!< @brief Position of new appended error message. */
   int handled;            /*!< @brief Whether the error has been handled. */
   int reraise;            /*!< @brief Error value to reraise. */
   ErrTryState state;      /*!< @brief Where we are in ErrTry.. ErrEnd. */