Better error handling

libzim/lib.cxx

@@ -25,6 +25,7 @@
 
 #include "wrapper_api.h"
 
+#include <cstdlib>
 #include <iostream>
 #include <zim/writer/url.h>
 #include <zim/blob.h>
@@ -62,11 +63,11 @@ std::string ZimArticleWrapper::callCythonReturnString(std::string methodName) co
     if (!this->m_obj)
         throw std::runtime_error("Python object not set");
 
-    int error;
+    std::string error;
 
     std::string ret_val = string_cy_call_fct(this->m_obj, methodName, &error);
-    if (error)
-        throw std::runtime_error("The pure virtual function " + methodName + " must be override");
+    if (!error.empty())
+        throw std::runtime_error(error);
 
     return ret_val;
 }
@@ -76,11 +77,11 @@ zim::Blob ZimArticleWrapper::callCythonReturnBlob(std::string methodName) const
     if (!this->m_obj)
         throw std::runtime_error("Python object not set");
 
-    int error;
+    std::string error;
 
     zim::Blob ret_val = blob_cy_call_fct(this->m_obj, methodName, &error);
-    if (error)
-        throw std::runtime_error("The pure virtual function " + methodName + " must be override");
+    if (!error.empty())
+        throw std::runtime_error(error);
 
     return ret_val;
 }
@@ -90,11 +91,11 @@ bool ZimArticleWrapper::callCythonReturnBool(std::string methodName) const
     if (!this->m_obj)
         throw std::runtime_error("Python object not set");
 
-    int error;
+    std::string error;
 
     bool ret_val = bool_cy_call_fct(this->m_obj, methodName, &error);
-    if (error)
-        throw std::runtime_error("The pure virtual function " + methodName + " must be override");
+    if (!error.empty())
+        throw std::runtime_error(error);
 
     return ret_val;
 }
@@ -104,11 +105,11 @@ uint64_t ZimArticleWrapper::callCythonReturnInt(std::string methodName) const
     if (!this->m_obj)
         throw std::runtime_error("Python object not set");
 
-    int error;
+    std::string error;
 
-    int ret_val = int_cy_call_fct(this->m_obj, methodName, &error);
-    if (error)
-        throw std::runtime_error("The pure virtual function " + methodName + " must be override");
+    int64_t ret_val = int_cy_call_fct(this->m_obj, methodName, &error);
+    if (!error.empty())
+        throw std::runtime_error(error);
 
     return ret_val;
 }

libzim/wrapper.pyx

@@ -32,6 +32,7 @@ from libcpp.memory cimport shared_ptr, make_shared, unique_ptr
 
 import pathlib
 import datetime
+import traceback
 
 
 #########################
@@ -98,44 +99,52 @@ cdef class ReadingBlob:
         self.view_count -= 1
 
 
-#------ Helper for pure virtual methods --------
-
-cdef get_article_method_from_object(object obj, string method, int *error) with gil:
-    try:
-        func = getattr(obj, method.decode('UTF-8'))
-    except AttributeError:
-        error[0] = 1
-        raise
-    else:
-        error[0] = 0
-        return func
-
 #------- ZimArticle pure virtual methods --------
 
 cdef public api:
-    string string_cy_call_fct(object obj, string method, int *error) with gil:
+    string string_cy_call_fct(object obj, string method, string *error) with gil:
         """Lookup and execute a pure virtual method on ZimArticle returning a string"""
-        func = get_article_method_from_object(obj, method, error)
-        ret_str = func()
-        return ret_str.encode('UTF-8')
-
-    wrapper.Blob blob_cy_call_fct(object obj, string method, int *error) with gil:
+        try:
+            func = getattr(obj, method.decode('UTF-8'))
+            ret_str = func()
+            return ret_str.encode('UTF-8')
+        except Exception as e:
+            error[0] = traceback.format_exc().encode('UTF-8')
+        return b""
+
+    wrapper.Blob blob_cy_call_fct(object obj, string method, string *error) with gil:
         """Lookup and execute a pure virtual method on ZimArticle returning a Blob"""
         cdef WritingBlob blob
 
-        func = get_article_method_from_object(obj, method, error)
-        blob = func()
-        return dereference(blob.c_blob)
+        try:
+            func = getattr(obj, method.decode('UTF-8'))
+            blob = func()
+            if blob is None:
+                raise RuntimeError("Blob is none")
+            return dereference(blob.c_blob)
+        except Exception as e:
+            error[0] = traceback.format_exc().encode('UTF-8')
 
-    bool bool_cy_call_fct(object obj, string method, int *error) with gil:
+        return Blob()
+
+    bool bool_cy_call_fct(object obj, string method, string *error) with gil:
         """Lookup and execute a pure virtual method on ZimArticle returning a bool"""
-        func = get_article_method_from_object(obj, method, error)
-        return func()
+        try:
+            func = getattr(obj, method.decode('UTF-8'))
+            return func()
+        except Exception as e:
+            error[0] = traceback.format_exc().encode('UTF-8')
+        return False
 
-    uint64_t int_cy_call_fct(object obj, string method, int *error) with gil:
+    uint64_t int_cy_call_fct(object obj, string method, string *error) with gil:
         """Lookup and execute a pure virtual method on ZimArticle returning an int"""
-        func = get_article_method_from_object(obj, method, error)
-        return <uint64_t> func()
+        try:
+            func = getattr(obj, method.decode('UTF-8'))
+            return <uint64_t>func()
+        except Exception as e:
+            error[0] = traceback.format_exc().encode('UTF-8')
+
+        return 0
 
 cdef class Creator:
     """ Zim Creator

libzim/writer.py

@@ -50,35 +50,35 @@ def __init__(self):
 
     def get_url(self) -> str:
         """ Full URL of article including namespace """
-        raise NotImplementedError
+        raise NotImplementedError("get_url must be implemented.")
 
     def get_title(self) -> str:
         """ Article title. Might be indexed and used in suggestions """
-        raise NotImplementedError
+        raise NotImplementedError("get_title must be implemented.")
 
     def is_redirect(self) -> bool:
         """ Whether this redirects to another article (cf. redirec_url) """
-        raise NotImplementedError
+        raise NotImplementedError("get_redirect must be implemented.")
 
     def get_mime_type(self) -> str:
         """ MIME-type of the article's content. A/ namespace reserved to text/html """
-        raise NotImplementedError
+        raise NotImplementedError("get_mime_type must be implemented.")
 
     def get_filename(self) -> str:
         """ Filename to get content from. Blank string "" if not used """
-        raise NotImplementedError
+        raise NotImplementedError("get_filename must be implemented.")
 
     def should_compress(self) -> bool:
         """ Whether the article's content should be compressed or not """
-        raise NotImplementedError
+        raise NotImplementedError("should_compress must be implemented.")
 
     def should_index(self) -> bool:
         """ Whether the article's content should be indexed or not """
-        raise NotImplementedError
+        raise NotImplementedError("should_index must be implemented.")
 
     def redirect_url(self) -> str:
         """ Full URL including namespace of another article """
-        raise NotImplementedError
+        raise NotImplementedError("redirect_url must be implemented.")
 
     def _get_data(self) -> Blob:
         """ Internal data-retrieval with a cache to the content's pointer
@@ -90,7 +90,7 @@ def _get_data(self) -> Blob:
 
     def get_data(self) -> Blob:
         """ Blob containing the complete content of the article """
-        raise NotImplementedError
+        raise NotImplementedError("get_data must be implemented.")
 
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}(url={self.get_url()}, title={self.get_title()})"

tests/test_libzim.py

@@ -16,9 +16,12 @@
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
-import pytest
+import sys
+import subprocess
 import pathlib
 
+import pytest
+
 from libzim.writer import Article, Blob, Creator
 from libzim.reader import File
 
@@ -188,3 +191,65 @@ def test_filename_param_types(tmpdir):
     with Creator(str(path), "welcome") as creator:
         assert creator.filename == path
         assert isinstance(creator.filename, pathlib.Path)
+
+
+def test_in_article_exceptions(tmpdir):
+    """ make sure we raise RuntimeError from article's virtual methods """
+
+    class BoolErrorArticle(SimpleArticle):
+        def is_redirect(self):
+            raise RuntimeError("OUPS Redirect")
+
+    class StringErrorArticle(SimpleArticle):
+        def get_url(self):
+            raise IOError
+
+    class BlobErrorArticle(SimpleArticle):
+        def get_data(self):
+            raise IOError
+
+    path, main_page = tmpdir / "test.zim", "welcome"
+    args = {"title": "Hello", "mime_type": "text/html", "content": "", "url": "welcome"}
+
+    with Creator(path, main_page) as zim_creator:
+        # make sure we can can exception of all types (except int, not used)
+        with pytest.raises(RuntimeError, match="OUPS Redirect"):
+            zim_creator.add_article(BoolErrorArticle(**args))
+        with pytest.raises(RuntimeError, match="in get_url"):
+            zim_creator.add_article(StringErrorArticle(**args))
+        with pytest.raises(RuntimeError, match="IOError"):
+            zim_creator.add_article(BlobErrorArticle(**args))
+        with pytest.raises(RuntimeError, match="NotImplementedError"):
+            zim_creator.add_article(Article())
+
+    # make sure we can catch it from outside creator
+    with pytest.raises(RuntimeError):
+        with Creator(path, main_page) as zim_creator:
+            zim_creator.add_article(BlobErrorArticle(**args))
+
+
+def test_dontcreatezim_onexception(tmpdir):
+    """ make sure we can prevent ZIM file creation (workaround missing cancel())
+
+        A new interpreter is instanciated to get a different memory space.
+        This workaround is not safe and may segfault at GC under some circumstances
+
+        Unless we get a proper cancel() on libzim, that's the only way to not create
+        a ZIM file on error """
+    path, main_page = tmpdir / "test.zim", "welcome"
+    pycode = f"""
+from libzim.writer import Creator
+from libzim.writer import Article
+class BlobErrorArticle(Article):
+    def get_data(self):
+        raise ValueError
+zim_creator = Creator("{path}", "{main_page}")
+try:
+    zim_creator.add_article(BlobErrorArticle(**args))
+except Exception:
+    zim_creator._closed = True
+"""
+
+    py = subprocess.run([sys.executable, "-c", pycode])
+    assert py.returncode == 0
+    assert not path.exists()