From cd8be655f1895957fb169cdf361297d9ecc40ec9 Mon Sep 17 00:00:00 2001
From: Scott Kostyshak <skostysh@lyx.org>
Date: Wed, 18 Mar 2015 16:51:12 -0400
Subject: [PATCH] Export/view a PDF even if error

A PDF is often still produced after a LaTeX error.

If there was an error when exporting a PDF, we now give an error
and the PDF (if it exists), where before we gave the error and
not the PDF. The GUI and command line behaviors are consistent:
in the GUI an error is given and the PDF is viewed; on the
command line, a non-zero exit code is given and a PDF is created.

This also solves what was in my mind an inconsistency: if the user
"updated" a document and there was an error, the resulting
PDF would be shown; but if the user viewed a document and there
was an error, the document would not be shown.

Note that this applies to all output formats, not just PDF.

For discussion, see:
https://www.mail-archive.com/lyx-devel@lists.lyx.org/msg186454.html
---
 src/Buffer.cpp | 13 +++++--------
 src/LaTeX.cpp  |  8 +++++++-
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index f9da416dfb..e045e01aa5 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -4119,12 +4119,10 @@ Buffer::ExportStatus Buffer::doExport(string const & target, bool put_in_tempdir
 		d->cloned_buffer_->d->errorLists[error_type] = d->errorLists[error_type];
 	}
 
-	if (!success)
-		return ExportConverterError;
 
 	if (put_in_tempdir) {
 		result_file = tmp_result_file.absFileName();
-		return ExportSuccess;
+		return success ? ExportSuccess : ExportConverterError;
 	}
 
 	if (dest_filename.empty())
@@ -4189,7 +4187,7 @@ Buffer::ExportStatus Buffer::doExport(string const & target, bool put_in_tempdir
 			formats.prettyName(format)));
 	}
 
-	return ExportSuccess;
+	return success ? ExportSuccess : ExportConverterError;
 }
 
 
@@ -4214,11 +4212,10 @@ Buffer::ExportStatus Buffer::preview(string const & format, bool includeall) con
 	}
 	// (2) export with included children only
 	ExportStatus const status = doExport(format, true, false, result_file);
-	if (status != ExportSuccess)
-		return status;
-	if (!formats.view(*this, FileName(result_file), format))
+	FileName const previewFile(result_file);
+	if (previewFile.exists() && !formats.view(*this, previewFile, format))
 		return PreviewError;
-	return PreviewSuccess;
+	return (status == ExportSuccess) ? PreviewSuccess : status;
 }
 
 
diff --git a/src/LaTeX.cpp b/src/LaTeX.cpp
index e4f8b4b490..ed59181e4b 100644
--- a/src/LaTeX.cpp
+++ b/src/LaTeX.cpp
@@ -110,6 +110,10 @@ LaTeX::LaTeX(string const & latex, OutputParams const & rp,
 
 void LaTeX::deleteFilesOnError() const
 {
+	// Note that we do not always call this function when there is an error.
+	// For example, if there is an error but an output file is produced we
+	// still would like to output (export/view) the file.
+
 	// What files do we have to delete?
 
 	// This will at least make latex do all the runs
@@ -236,7 +240,9 @@ int LaTeX::run(TeXErrors & terr)
 	}
 
 	if (scanres & ERRORS) {
-		deleteFilesOnError();
+		// We no longer run deleteFilesOnError() here
+		// because we now show a resulting PDF even if
+		// there was an error.
 		return scanres; // return on error
 	}