Try to give possible explanations when opening a preview fails

src/index/exefetcher.cpp

@@ -77,7 +77,8 @@ bool EXEDocFetcher::makesig(RclConfig* cnf, const Rcl::Doc& idoc, string& sig)
 }
 
 // Lookup bckid in the config and create an appropriate fetcher.
-EXEDocFetcher *exeDocFetcherMake(RclConfig *config, const string& bckid)
+std::unique_ptr<EXEDocFetcher> exeDocFetcherMake(RclConfig *config,
+                                                 const string& bckid)
 {
     // The config we only read once, not gonna change.
     static ConfSimple *bconf;
@@ -122,5 +123,5 @@ EXEDocFetcher *exeDocFetcherMake(RclConfig *config, const string& bckid)
                " not found in exec path or filters dir\n");
         return 0;
     }
-    return new EXEDocFetcher(m);
+    return std::unique_ptr<EXEDocFetcher>(new EXEDocFetcher(m));
 }

src/index/exefetcher.h

@@ -17,6 +17,7 @@
 #ifndef _EXEFETCHER_H_INCLUDED_
 #define _EXEFETCHER_H_INCLUDED_
 
+#include <memory>
 #include "fetcher.h"
 
 class RclConfig;
@@ -35,6 +36,7 @@ class RclConfig;
  * query time for previewing and opening the document.
  */
 class EXEDocFetcher : public DocFetcher {
+public:
     class Internal;
     EXEDocFetcher(const Internal&);
     virtual ~EXEDocFetcher() {}
@@ -42,12 +44,14 @@ class EXEDocFetcher : public DocFetcher {
     virtual bool fetch(RclConfig* cnf, const Rcl::Doc& idoc, RawDoc& out);
     /** Calls stat to retrieve file signature data */
     virtual bool makesig(RclConfig* cnf, const Rcl::Doc& idoc,std::string& sig);
-    friend EXEDocFetcher *exeDocFetcherMake(RclConfig *, const std::string&);
+    friend std::unique_ptr<EXEDocFetcher>
+    exeDocFetcherMake(RclConfig *, const std::string&);
 private:
     Internal *m;
 };
 
 // Lookup bckid in the config and create an appropriate fetcher.
-EXEDocFetcher *exeDocFetcherMake(RclConfig *config, const std::string& bckid);
+std::unique_ptr<EXEDocFetcher> exeDocFetcherMake(RclConfig *config,
+                                                 const std::string& bckid);
 
 #endif /* _EXEFETCHER_H_INCLUDED_ */

src/index/fetcher.cpp

@@ -16,6 +16,8 @@
  */
 #include "autoconfig.h"
 
+#include <memory>
+
 #include "log.h"
 #include "rclconfig.h"
 #include "fetcher.h"
@@ -23,22 +25,23 @@
 #include "webqueuefetcher.h"
 #include "exefetcher.h"
 
-DocFetcher *docFetcherMake(RclConfig *config, const Rcl::Doc& idoc)
+std::unique_ptr<DocFetcher> docFetcherMake(RclConfig *config,
+                                           const Rcl::Doc& idoc)
 {
     if (idoc.url.empty()) {
         LOGERR("docFetcherMakeg:: no url in doc!\n" );
-        return 0;
+        return std::unique_ptr<DocFetcher>();
     }
     string backend;
     idoc.getmeta(Rcl::Doc::keybcknd, &backend);
     if (backend.empty() || !backend.compare("FS")) {
-	return new FSDocFetcher;
+	return std::unique_ptr<DocFetcher>(new FSDocFetcher);
 #ifndef DISABLE_WEB_INDEXER
     } else if (!backend.compare("BGL")) {
-	return new WQDocFetcher;
+	return std::unique_ptr<DocFetcher>(new WQDocFetcher);
 #endif
     } else {
-        DocFetcher *f = exeDocFetcherMake(config, backend);
+        std::unique_ptr<DocFetcher> f(exeDocFetcherMake(config, backend));
         if (!f) {
             LOGERR("DocFetcherFactory: unknown backend [" << backend << "]\n");
         }

src/index/fetcher.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2012 J.F.Dockes
+/* Copyright (C) 2012-2019 J.F.Dockes
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
  *   the Free Software Foundation; either version 2 of the License, or
@@ -19,6 +19,7 @@
 
 #include "safesysstat.h"
 #include <string>
+#include <memory>
 
 #include "rcldoc.h"
 
@@ -45,12 +46,12 @@ class RclConfig;
 class DocFetcher {
 public:
     /** A RawDoc is the data for a document-holding entity either as a
-       memory block, or pointed to by a file name */
+        memory block, or pointed to by a file name */
     struct RawDoc {
-	enum RawDocKind {RDK_FILENAME, RDK_DATA, RDK_DATADIRECT};
-	RawDocKind kind;
-	std::string data; // Doc data or file name
-	struct stat st; // Only used if RDK_FILENAME
+        enum RawDocKind {RDK_FILENAME, RDK_DATA, RDK_DATADIRECT};
+        RawDocKind kind;
+        std::string data; // Doc data or file name
+        struct stat st; // Only used if RDK_FILENAME
     };
 
     /** 
@@ -73,11 +74,16 @@ public:
      */
     virtual bool makesig(RclConfig* cnf, const Rcl::Doc& idoc,
                          std::string& sig) = 0;
+    enum Reason{FetchOk, FetchNotExist, FetchNoPerm, FetchOther};
+    virtual Reason testAccess(RclConfig* cnf, const Rcl::Doc& idoc) {
+        return FetchOther;
+    }
     virtual ~DocFetcher() {}
 };
 
 /** Return an appropriate fetcher object given the backend string 
  * identifier inside idoc*/
-DocFetcher *docFetcherMake(RclConfig *config, const Rcl::Doc& idoc);
+std::unique_ptr<DocFetcher> docFetcherMake(RclConfig *config,
+                                           const Rcl::Doc& idoc);
 
 #endif /* _FETCHER_H_INCLUDED_ */

src/index/fsfetcher.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2012 J.F.Dockes
+/* Copyright (C) 2012-2019 J.F.Dockes
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
  *   the Free Software Foundation; either version 2 of the License, or
@@ -28,31 +28,32 @@
 
 using std::string;
 
-static bool urltopath(RclConfig* cnf,
-		      const Rcl::Doc& idoc, string& fn, struct stat& st)
+static DocFetcher::Reason urltopath(RclConfig* cnf, const Rcl::Doc& idoc,
+                                    string& fn, struct stat& st)
 {
     // The url has to be like file://
     fn = fileurltolocalpath(idoc.url);
     if (fn.empty()) {
-	LOGERR("FSDocFetcher::fetch/sig: non fs url: ["  << (idoc.url) << "]\n" );
-	return false;
+        LOGERR("FSDocFetcher::fetch/sig: non fs url: [" << idoc.url << "]\n");
+        return DocFetcher::FetchOther;
     }
     cnf->setKeyDir(path_getfather(fn));
     bool follow = false;
     cnf->getConfParam("followLinks", &follow);
 
     if (path_fileprops(fn, &st, follow) < 0) {
-	LOGERR("FSDocFetcher::fetch: stat errno "  << (errno) << " for ["  << (fn) << "]\n" );
-	return false;
+        LOGERR("FSDocFetcher::fetch: stat errno " << errno << " for [" << fn
+               << "]\n");
+        return DocFetcher::FetchNotExist;
     }
-    return true;
+    return DocFetcher::FetchOk;
 }
 
 bool FSDocFetcher::fetch(RclConfig* cnf, const Rcl::Doc& idoc, RawDoc& out)
 {
     string fn;
-    if (!urltopath(cnf, idoc, fn, out.st))
-	return false;
+    if (urltopath(cnf, idoc, fn, out.st) != DocFetcher::FetchOk)
+        return false;
     out.kind = RawDoc::RDK_FILENAME;
     out.data = fn;
     return true;
@@ -62,10 +63,24 @@ bool FSDocFetcher::makesig(RclConfig* cnf, const Rcl::Doc& idoc, string& sig)
 {
     string fn;
     struct stat st;
-    if (!urltopath(cnf, idoc, fn, st))
-	return false;
+    if (urltopath(cnf, idoc, fn, st) != DocFetcher::FetchOk)
+        return false;
     FsIndexer::makesig(&st, sig);
     return true;
 }
 
-
+DocFetcher::Reason FSDocFetcher::testAccess(RclConfig* cnf, const Rcl::Doc& idoc)
+{
+    string fn;
+    struct stat st;
+    DocFetcher::Reason reason = urltopath(cnf, idoc, fn, st);
+    if (reason != DocFetcher::FetchOk) {
+        return reason;
+    }
+    if (!path_readable(fn)) {
+        return DocFetcher::FetchNoPerm;
+    }
+    // We have no way to know if the file is fully readable without
+    // trying (local Windows locks), which would take too much time.
+    return DocFetcher::FetchOther;
+}

src/index/fsfetcher.h

@@ -28,6 +28,7 @@ class FSDocFetcher : public DocFetcher{
     
     /** Calls stat to retrieve file signature data */
     virtual bool makesig(RclConfig* cnf,const Rcl::Doc& idoc, std::string& sig);
+    virtual DocFetcher::Reason testAccess(RclConfig* cnf, const Rcl::Doc& idoc);
     virtual ~FSDocFetcher() {}
 };