refactor! split SubplotError::IoError into more specific errors

Replace SubplotError::IoError with ::Spawn, ::WriteToChild,
::WaitForChild, ::ReadFile, ::CreateFile, ::Writefile.

IoError was a catchall error and as such, so generic that it didn't
help the user to figure out what actually is wrong. For example, there
was no indication what operation was attempted or on what file. The
new error variants are specific.

Sponsored-by: author

1 files changed, 9 insertions, 4 deletions

diff --git a/src/codegen.rs b/src/codegen.rs
index b940b4d..5c4255f 100644
--- a/src/codegen.rs
+++ b/src/codegen.rs
@@ -62,12 +62,15 @@ fn tera(tmplspec: &TemplateSpec, templatename: &str) -> Result<Tera, SubplotErro
     let dirname = tmplspec.template_filename().parent().unwrap();
     for helper in tmplspec.helpers() {
         let helper_path = dirname.join(helper);
-        let helper_content = resource::read_as_string(helper_path, Some(templatename))?;
+        let helper_content = resource::read_as_string(&helper_path, Some(templatename))
+            .map_err(|err| SubplotError::ReadFile(helper_path.clone(), err))?;
         let helper_name = helper.display().to_string();
         tera.add_raw_template(&helper_name, &helper_content)
             .map_err(|err| SubplotError::TemplateError(helper_name.to_string(), err))?;
     }
-    let template = resource::read_as_string(tmplspec.template_filename(), Some(templatename))?;
+    let path = tmplspec.template_filename();
+    let template = resource::read_as_string(path, Some(templatename))
+        .map_err(|err| SubplotError::ReadFile(path.to_path_buf(), err))?;
     tera.add_raw_template("template", &template)
         .map_err(|err| {
             SubplotError::TemplateError(tmplspec.template_filename().display().to_string(), err)
@@ -76,8 +79,10 @@ fn tera(tmplspec: &TemplateSpec, templatename: &str) -> Result<Tera, SubplotErro
 }
 
 fn write(filename: &Path, content: &str) -> Result<(), SubplotError> {
-    let mut f: File = File::create(filename)?;
-    f.write_all(content.as_bytes())?;
+    let mut f: File = File::create(filename)
+        .map_err(|err| SubplotError::CreateFile(filename.to_path_buf(), err))?;
+    f.write_all(content.as_bytes())
+        .map_err(|err| SubplotError::WriteFile(filename.to_path_buf(), err))?;
     Ok(())
 }