PyAPI: support retrieving the exception when running a string

- Optionally get the error as a single line.
- Support access the error as an allocated string.
- PyC_ExceptionBuffer_Simple was always printing to the `stdout` while
  PyC_ExceptionBuffer didn't, now either print to the output.

Without this, callers are unable to do anything with the error string.

3 files changed, 63 insertions, 29 deletions

diff --git a/source/blender/python/BPY_extern_run.h b/source/blender/python/BPY_extern_run.h
index 5f12ada4ff2..b65b5d61b9d 100644
--- a/source/blender/python/BPY_extern_run.h
+++ b/source/blender/python/BPY_extern_run.h
@@ -42,27 +42,43 @@ bool BPY_run_text(struct bContext *C,
 bool BPY_run_string_exec(struct bContext *C, const char *imports[], const char *expr);
 bool BPY_run_string_eval(struct bContext *C, const char *imports[], const char *expr);
 
+/**
+ * \note When this struct is passed in as NULL,
+ * print errors to the `stdout` and clear.
+ */
+struct BPy_RunErrInfo {
+  /** Brief text, single line (can show this in status bar for e.g.). */
+  bool use_single_line_error;
+
+  /** Report with optional prefix (when non-NULL). */
+  struct ReportList *reports;
+  const char *report_prefix;
+
+  /** Allocated exception text (assign when non-NULL). */
+  char **r_string;
+};
+
 /* Run, evaluating to fixed type result. */
 bool BPY_run_string_as_number(struct bContext *C,
                               const char *imports[],
                               const char *expr,
-                              const char *report_prefix,
+                              struct BPy_RunErrInfo *err_info,
                               double *r_value);
 bool BPY_run_string_as_intptr(struct bContext *C,
                               const char *imports[],
                               const char *expr,
-                              const char *report_prefix,
+                              struct BPy_RunErrInfo *err_info,
                               intptr_t *r_value);
 bool BPY_run_string_as_string_and_size(struct bContext *C,
                                        const char *imports[],
                                        const char *expr,
-                                       const char *report_prefix,
+                                       struct BPy_RunErrInfo *err_info,
                                        char **r_value,
                                        size_t *r_value_size);
 bool BPY_run_string_as_string(struct bContext *C,
                               const char *imports[],
                               const char *expr,
-                              const char *report_prefix,
+                              struct BPy_RunErrInfo *err_info,
                               char **r_value);
 
 #ifdef __cplusplus
diff --git a/source/blender/python/generic/py_capi_utils.c b/source/blender/python/generic/py_capi_utils.c
index 78f5b9ba2cc..9824d5f17c4 100644
--- a/source/blender/python/generic/py_capi_utils.c
+++ b/source/blender/python/generic/py_capi_utils.c
@@ -733,7 +733,6 @@ PyObject *PyC_ExceptionBuffer_Simple(void)
 
   PyErr_Restore(error_type, error_value, error_traceback);
 
-  PyErr_Print();
   PyErr_Clear();
   return string_io_buf;
 }
diff --git a/source/blender/python/intern/bpy_interface_run.c b/source/blender/python/intern/bpy_interface_run.c
index a7593ae7d79..f7272a87a17 100644
--- a/source/blender/python/intern/bpy_interface_run.c
+++ b/source/blender/python/intern/bpy_interface_run.c
@@ -31,6 +31,7 @@
 
 #include "BKE_context.h"
 #include "BKE_main.h"
+#include "BKE_report.h"
 #include "BKE_text.h"
 
 #include "DNA_text_types.h"
@@ -294,13 +295,47 @@ bool BPY_run_string_exec(bContext *C, const char *imports[], const char *expr)
  * in code that doesn't deal with Python data-types.
  * \{ */
 
+static void run_string_handle_error(struct BPy_RunErrInfo *err_info)
+{
+  if (err_info == NULL) {
+    PyErr_Print();
+    PyErr_Clear();
+    return;
+  }
+
+  /* Signal to do nothing. */
+  if (!(err_info->reports || err_info->r_string)) {
+    PyErr_Clear();
+    return;
+  }
+
+  PyObject *py_err_str = err_info->use_single_line_error ? PyC_ExceptionBuffer_Simple() :
+                                                           PyC_ExceptionBuffer();
+  const char *err_str = py_err_str ? PyUnicode_AsUTF8(py_err_str) : "Unable to extract exception";
+
+  if (err_info->reports != NULL) {
+    if (err_info->report_prefix) {
+      BKE_reportf(err_info->reports, RPT_ERROR, "%s: %s", err_info->report_prefix, err_str);
+    }
+    else {
+      BKE_report(err_info->reports, RPT_ERROR, err_str);
+    }
+  }
+
+  if (err_info->r_string != NULL) {
+    *err_info->r_string = BLI_strdup(err_str);
+  }
+
+  Py_XDECREF(py_err_str);
+}
+
 /**
  * \return success
  */
 bool BPY_run_string_as_number(bContext *C,
                               const char *imports[],
                               const char *expr,
-                              const char *report_prefix,
+                              struct BPy_RunErrInfo *err_info,
                               double *r_value)
 {
   PyGILState_STATE gilstate;
@@ -320,12 +355,7 @@ bool BPY_run_string_as_number(bContext *C,
   ok = PyC_RunString_AsNumber(imports, expr, "<expr as number>", r_value);
 
   if (ok == false) {
-    if (report_prefix != NULL) {
-      BPy_errors_to_report_ex(CTX_wm_reports(C), report_prefix, false, false);
-    }
-    else {
-      PyErr_Clear();
-    }
+    run_string_handle_error(err_info);
   }
 
   bpy_context_clear(C, &gilstate);
@@ -339,7 +369,7 @@ bool BPY_run_string_as_number(bContext *C,
 bool BPY_run_string_as_string_and_size(bContext *C,
                                        const char *imports[],
                                        const char *expr,
-                                       const char *report_prefix,
+                                       struct BPy_RunErrInfo *err_info,
                                        char **r_value,
                                        size_t *r_value_size)
 {
@@ -357,12 +387,7 @@ bool BPY_run_string_as_string_and_size(bContext *C,
   ok = PyC_RunString_AsStringAndSize(imports, expr, "<expr as str>", r_value, r_value_size);
 
   if (ok == false) {
-    if (report_prefix != NULL) {
-      BPy_errors_to_report_ex(CTX_wm_reports(C), false, false, report_prefix);
-    }
-    else {
-      PyErr_Clear();
-    }
+    run_string_handle_error(err_info);
   }
 
   bpy_context_clear(C, &gilstate);
@@ -373,12 +398,11 @@ bool BPY_run_string_as_string_and_size(bContext *C,
 bool BPY_run_string_as_string(bContext *C,
                               const char *imports[],
                               const char *expr,
-                              const char *report_prefix,
+                              struct BPy_RunErrInfo *err_info,
                               char **r_value)
 {
   size_t value_dummy_size;
-  return BPY_run_string_as_string_and_size(
-      C, imports, expr, report_prefix, r_value, &value_dummy_size);
+  return BPY_run_string_as_string_and_size(C, imports, expr, err_info, r_value, &value_dummy_size);
 }
 
 /**
@@ -389,7 +413,7 @@ bool BPY_run_string_as_string(bContext *C,
 bool BPY_run_string_as_intptr(bContext *C,
                               const char *imports[],
                               const char *expr,
-                              const char *report_prefix,
+                              struct BPy_RunErrInfo *err_info,
                               intptr_t *r_value)
 {
   BLI_assert(r_value && expr);
@@ -406,12 +430,7 @@ bool BPY_run_string_as_intptr(bContext *C,
   ok = PyC_RunString_AsIntPtr(imports, expr, "<expr as intptr>", r_value);
 
   if (ok == false) {
-    if (report_prefix != NULL) {
-      BPy_errors_to_report_ex(CTX_wm_reports(C), report_prefix, false, false);
-    }
-    else {
-      PyErr_Clear();
-    }
+    run_string_handle_error(err_info);
   }
 
   bpy_context_clear(C, &gilstate);