Make Page an interface

The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue  #5074, "pages from other data sources".

But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.

Most notable changes:

* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
  This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
  This improves the taxonomy template `.Title` situation and make common template constructs much simpler.

See #5074
Fixes #5763
Fixes #5758
Fixes #5090
Fixes #5204
Fixes #4695
Fixes #5607
Fixes #5707
Fixes #5719
Fixes #3113
Fixes #5706
Fixes #5767
Fixes #5723
Fixes #5769
Fixes #5770
Fixes #5771
Fixes #5759
Fixes #5776
Fixes #5777
Fixes #5778

1 files changed, 7 insertions, 3 deletions

diff --git a/commands/import_jekyll.go b/commands/import_jekyll.go
index d3301b48f..1d37cfd9d 100644
--- a/commands/import_jekyll.go
+++ b/commands/import_jekyll.go
@@ -1,4 +1,4 @@
-// Copyright 2016 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -340,7 +340,7 @@ func copyDir(source string, dest string) error {
 	if err != nil {
 		return err
 	}
-	entries, err := ioutil.ReadDir(source)
+	entries, _ := ioutil.ReadDir(source)
 	for _, entry := range entries {
 		sfp := filepath.Join(source, entry.Name())
 		dfp := filepath.Join(dest, entry.Name())
@@ -373,6 +373,10 @@ func (i *importCmd) copyJekyllFilesAndFolders(jekyllRoot, dest string, jekyllPos
 		return err
 	}
 	entries, err := ioutil.ReadDir(jekyllRoot)
+	if err != nil {
+		return err
+	}
+
 	for _, entry := range entries {
 		sfp := filepath.Join(jekyllRoot, entry.Name())
 		dfp := filepath.Join(dest, entry.Name())
@@ -464,7 +468,7 @@ func convertJekyllPost(s *hugolib.Site, path, relPath, targetDir string, draft b
 
 	fs := hugofs.Os
 	if err := helpers.WriteToDisk(targetFile, strings.NewReader(content), fs); err != nil {
-		return fmt.Errorf("Failed to save file %q:", filename)
+		return fmt.Errorf("failed to save file %q: %s", filename, err)
 	}
 
 	return nil