From 95bc7f84bbe909c69783f9ae379af2230ddc0739 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Sun, 24 May 2020 19:46:20 +0300
Subject: fix: report name of missing bindings or functions file in error msg

---
 src/bindings.rs |  3 ++-
 src/codegen.rs  |  6 ++++--
 src/error.rs    |  8 ++++++++
 subplot.md      | 40 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/src/bindings.rs b/src/bindings.rs
index 9c0df9e..4233528 100644
--- a/src/bindings.rs
+++ b/src/bindings.rs
@@ -316,7 +316,8 @@ impl Bindings {
     where
         P: AsRef<Path>,
     {
-        let mut f = File::open(filename)?;
+        let mut f = File::open(filename.as_ref())
+            .map_err(|e| SubplotError::BindingsFileNotFound(filename.as_ref().into(), e))?;
         let mut yaml = String::new();
         f.read_to_string(&mut yaml)?;
         self.add_from_yaml(&yaml)?;
diff --git a/src/codegen.rs b/src/codegen.rs
index db31765..9895783 100644
--- a/src/codegen.rs
+++ b/src/codegen.rs
@@ -1,4 +1,4 @@
-use crate::{Document, TemplateSpec};
+use crate::{Document, SubplotError, TemplateSpec};
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::prelude::{Read, Write};
@@ -44,7 +44,9 @@ fn context(doc: &mut Document) -> Result<Context> {
     let funcs_filenames = doc.meta().functions_filenames();
     let mut funcs = String::new();
     for filename in funcs_filenames {
-        funcs.push_str(&cat(filename)?);
+        let content =
+            cat(filename).map_err(|e| SubplotError::FunctionsFileNotFound(filename.into(), e))?;
+        funcs.push_str(&content);
     }
     context.insert("functions", &funcs);
 
diff --git a/src/error.rs b/src/error.rs
index 0057f37..f988c86 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -6,6 +6,14 @@ use thiserror::Error;
 /// Define all the kinds of errors any part of this crate can return.
 #[derive(Debug, Error)]
 pub enum SubplotError {
+    /// Subplot could not find a file named as a bindings file.
+    #[error("binding file could not be found: {0}: {1}")]
+    BindingsFileNotFound(PathBuf, std::io::Error),
+
+    /// Subplot could not find a file named as a functions file.
+    #[error("functions file could not be found: {0}: {1}")]
+    FunctionsFileNotFound(PathBuf, anyhow::Error),
+
     /// The simple pattern contains a stray { or }.
     #[error("simple pattern contains a stray {{ or }}")]
     StrayBraceInSimplePattern(String),
diff --git a/subplot.md b/subplot.md
index bcd4eb9..b2cdecf 100644
--- a/subplot.md
+++ b/subplot.md
@@ -1458,6 +1458,46 @@ and file mtime.html contains "Geoffrey Butler"
 and file mtime.html contains "2020-02-26 07:53"
 ~~~
 
+### Missing bindings file
+
+If a bindings file is missing, the error message should name the
+missing file.
+
+~~~scenario
+given file missing-binding.md
+when I try to run sp-docgen missing-binding.md -o foo.htmlh
+then exit code is non-zero
+and stderr matches /: missing-binding.yaml:/
+~~~
+
+~~~{#missing-binding.md .file .markdown .numberLines}
+---
+title: Missing binding
+bindings: missing-binding.yaml
+...
+~~~
+
+### Missing functions file
+
+If a functions file is missing, the error message should name the
+missing file.
+
+~~~scenario
+given file missing-functions.md
+and file b.yaml
+when I try to run sp-codegen --run missing-functions.md -o foo.py
+then exit code is non-zero
+and stderr matches /: missing-functions.py:/
+~~~
+
+~~~{#missing-functions.md .file .markdown .numberLines}
+---
+title: Missing functions
+bindings: b.yaml
+functions: missing-functions.py
+...
+~~~
+
 ### Extracting metadata from a document
 
 The **sp-meta** program extracts metadata from a document. It is
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