Add context to errors

Remove `unwrap`s and add context to errors with 'anyhow'.

3 files changed, 38 insertions, 11 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e20b14b..20315d7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -7,6 +7,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
 [[package]]
+name = "anyhow"
+version = "1.0.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28b2cd92db5cbd74e8e5028f7e27dd7aa3090e89e4f2a197cc7c8dfb69c7063b"
+
+[[package]]
 name = "autocfg"
 version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -245,6 +251,7 @@ dependencies = [
 name = "pdf-form-replace-font"
 version = "0.0.1"
 dependencies = [
+ "anyhow",
  "getopts",
  "lopdf",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 4f190e2..91ced45 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,5 +4,6 @@ version = "0.0.1"
 edition = "2018"
 
 [dependencies]
+anyhow = "1.0.40"
 getopts = "0.2.21"
 lopdf = "0.26.0"
diff --git a/src/main.rs b/src/main.rs
index 7c1e077..492707f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,10 +1,20 @@
+use anyhow::{self, Context};
 use getopts::Options;
 use lopdf::{Document, Object};
 
 use std::env;
 
 
-fn main() -> Result<(), Box<dyn std::error::Error>> {
+fn main() {
+    match run() {
+        Ok(_) => (),
+        Err(e) => {
+            eprintln!("error: {}", e);
+        },
+    };
+}
+
+fn run () -> Result<(), anyhow::Error> {
     let args: Vec<String> = env::args().collect();
 
     let mut opts = Options::new();
@@ -23,27 +33,34 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         &opt_matches.free[0]
     };
 
-    let find = opt_matches.opt_str("find").unwrap();
-    let replace = opt_matches.opt_str("replace").unwrap();
-    let output_pdf = opt_matches.opt_str("output").unwrap_or("-".to_owned());
+    let find = opt_matches.opt_str("find")
+        .ok_or(anyhow::anyhow!("no original font"))?;
+    let replace = opt_matches.opt_str("replace")
+        .ok_or(anyhow::anyhow!("no replacement font"))?;
+    let output_pdf = opt_matches.opt_str("output")
+        .unwrap_or("-".to_owned());
 
     let mut doc = if input_pdf == "=" {
-        Document::load_from(&mut std::io::stdin()).unwrap()
+        Document::load_from(&mut std::io::stdin())
+            .context("failed reading from stdin")?
     } else {
-        Document::load(input_pdf).unwrap()
+        Document::load(input_pdf)
+            .with_context(|| format!("failed to read PDF '{}'", input_pdf))?
     };
 
     for (_, mut obj) in &mut doc.objects {
         match &mut obj {
             Object::Dictionary(ref mut d) => {
                 for (k, v) in d.iter_mut() {
-                    let key = std::str::from_utf8(k).unwrap();
+                    let key = std::str::from_utf8(k)
+                        .context("unable to convert PDF object key to UTF-8")?;
 
                     if key == "DA" {
-                        let properties = v.as_str_mut().unwrap();
+                        let properties = v.as_str_mut()
+                            .context("unable to get properties of form field")?;
 
                         let new_properties = std::str::from_utf8(properties)
-                            .unwrap()
+                            .context("unable to convert form field properties to UTF-8")?
                             .replace(&find, &replace);
 
                         *properties = new_properties.into_bytes();
@@ -55,9 +72,11 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     if output_pdf == "-" {
-        doc.save_to(&mut std::io::stdout()).unwrap();
+        doc.save_to(&mut std::io::stdout())
+            .context("failed writing to stdout")?;
     } else {
-        doc.save(output_pdf).unwrap();
+        doc.save(&output_pdf)
+            .with_context(|| format!("failed to write PDF '{}'", output_pdf))?;
     }
 
     Ok(())