From e889ebdef94434109e63847e39d0c979569c44c0 Mon Sep 17 00:00:00 2001
From: Daniel Silverstone <dsilvers@digital-scurf.org>
Date: Thu, 21 May 2020 16:31:36 +0100
Subject: feat: Add linting for add-newline attribute

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>
---
 src/ast.rs   | 41 +++++++++++++++++++++++++++++++++++++++++
 src/error.rs | 14 ++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/src/ast.rs b/src/ast.rs
index f627178..bc3547d 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -89,6 +89,12 @@ impl<'a> Document {
     {
         let mut ast: Pandoc = serde_json::from_str(json)?;
         let meta = Metadata::new(basedir, &ast)?;
+        let mut linter = LintingVisitor::default();
+        linter.walk_pandoc(&mut ast);
+        if !linter.issues.is_empty() {
+            // Currently we can't really return more than one error so return one
+            return Err(linter.issues.remove(0));
+        }
         let files = DataFiles::new(&mut ast);
         Ok(Document::new(markdowns, ast, meta, files))
     }
@@ -1077,6 +1083,41 @@ impl MutVisitor for BlockClassVisitor {
     }
 }
 
+#[derive(Default)]
+struct LintingVisitor {
+    issues: Vec<SubplotError>,
+}
+
+impl MutVisitor for LintingVisitor {
+    fn visit_vec_block(&mut self, vec_block: &mut Vec<Block>) {
+        for block in vec_block {
+            match block {
+                Block::CodeBlock(attr, _) => {
+                    if is_class(attr, "file") {
+                        let newlines: Vec<_> = find_attr_kv(&attr, "add-newline").collect();
+                        match newlines.len() {
+                            0 => {}
+                            1 => match newlines[0].to_ascii_lowercase().as_ref() {
+                                "auto" | "yes" | "no" => {}
+                                _ => self.issues.push(SubplotError::UnrecognisedAddNewline(
+                                    get_filename(&attr),
+                                    newlines[0].to_owned(),
+                                )),
+                            },
+                            _ => self.issues.push(SubplotError::RepeatedAddNewlineAttribute(
+                                get_filename(&attr),
+                            )),
+                        }
+                    }
+                }
+                _ => {
+                    self.visit_block(block);
+                }
+            }
+        }
+    }
+}
+
 /// Get the base directory given the name of the markdown file.
 ///
 /// All relative filename, such as bindings files, are resolved
diff --git a/src/error.rs b/src/error.rs
index 60c850e..0057f37 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -126,6 +126,20 @@ pub enum SubplotError {
     #[error("Duplicate embedded file name: {0}")]
     DuplicateEmbeddedFilename(String),
 
+    /// Embedded file has more than one `add-newline` attribute
+    ///
+    /// The `add-newline` attribute can only be specified once for any given
+    /// embedded file
+    #[error("Embedded file {0} has more than one `add-newline` attribute")]
+    RepeatedAddNewlineAttribute(String),
+
+    /// Unrecognised `add-newline` attribute value on an embedded file
+    ///
+    /// The `add-newline` attribute can only take the values `auto`, `yes`,
+    /// and `no`.
+    #[error("Embedded file {0} has unrecognised `add-newline={}` - valid values are auto/yes/no")]
+    UnrecognisedAddNewline(String, String),
+
     /// Couldn't determine base directory from input file name.
     ///
     /// Subplot needs to to determine the base directory for files
-- 
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