Use invariant instead of unwrap and expect

Add the `Invariant` trait, which provides `Invariant::invariant` and
`Invariant::invariant_unwrap` methods, and use them instead of unwrap
and expect.

I think these methods are a bit clearer than `unwrap` and `expect`,
since they more clearly document intent, i.e. that the thing passed to
`invariant` should be a description of an invariant that should always
be true, and should provide better error messages.

Replace uses of `unwrap` and `expect` with `invariant`.

type: reform
fixes:
- https://github.com/casey/intermodal/issues/167

CHANGELOG.md

@@ -4,7 +4,8 @@ Changelog
 
 UNRELEASED - 2020-04-18
 -----------------------
-- :white_check_mark: [`xxxxxxxxxxxx`](https://github.com/casey/intermodal/commits/master) Test that globs match torrent contents - Fixes [#377](https://github.com/casey/intermodal/issues/377) - _Casey Rodarmor <casey@rodarmor.com>_
+- :art: [`xxxxxxxxxxxx`](https://github.com/casey/intermodal/commits/master) Use `invariant` instead of `unwrap` and `expect` - Fixes [#167](https://github.com/casey/intermodal/issues/167) - _Casey Rodarmor <casey@rodarmor.com>_
+- :white_check_mark: [`faf46c0f0e6f`](https://github.com/casey/intermodal/commit/faf46c0f0e6fd4e4f8b504d414a3bf02d7d68e4a) Test that globs match torrent contents - Fixes [#377](https://github.com/casey/intermodal/issues/377) - _Casey Rodarmor <casey@rodarmor.com>_
 - :books: [`0a754d0bcfcf`](https://github.com/casey/intermodal/commit/0a754d0bcfcfd65127d7b6e78d41852df78d3ea2) Add manual Arch install link - Fixes [#373](https://github.com/casey/intermodal/issues/373) - _Casey Rodarmor <casey@rodarmor.com>_
 - :art: [`0a870ed2ee2c`](https://github.com/casey/intermodal/commit/0a870ed2ee2cca79fddb9940fb879354468deb4d) Get current time early when creating torrents - Fixes [#207](https://github.com/casey/intermodal/issues/207) - _Casey Rodarmor <casey@rodarmor.com>_
 - :books: [`9098d3684032`](https://github.com/casey/intermodal/commit/9098d368403232a07684cae8c0b9b1f1383dd2ce) Readme improvements - _Casey Rodarmor <casey@rodarmor.com>_

src/common.rs

@@ -55,8 +55,9 @@ pub(crate) use crate::{consts, error, host_port_parse_error};
 
 // traits
 pub(crate) use crate::{
-  input_stream::InputStream, into_u64::IntoU64, into_usize::IntoUsize, path_ext::PathExt,
+  input_stream::InputStream, into_u64::IntoU64, into_usize::IntoUsize, invariant::Invariant,
-  platform_interface::PlatformInterface, print::Print, reckoner::Reckoner, step::Step,
+  path_ext::PathExt, platform_interface::PlatformInterface, print::Print, reckoner::Reckoner,
+  step::Step,
 };
 
 // structs and enums

src/error.rs

@@ -173,7 +173,10 @@ impl From<SystemTimeError> for Error {
 
 impl From<walkdir::Error> for Error {
   fn from(walkdir_error: walkdir::Error) -> Self {
-    let path = walkdir_error.path().unwrap().to_owned();
+    let path = walkdir_error
+      .path()
+      .invariant_unwrap("Walkdir errors always have path")
+      .to_owned();
 
     if let Some(source) = walkdir_error.into_io_error() {
       Self::Filesystem { source, path }

src/host_port.rs

@@ -19,11 +19,18 @@ impl FromStr for HostPort {
       $
       ",
     )
-    .unwrap();
+    .invariant_unwrap("regex is valid");
 
     if let Some(captures) = socket_address_re.captures(text) {
-      let host_text = captures.name("host").unwrap().as_str();
+      let host_text = captures
-      let port_text = captures.name("port").unwrap().as_str();
+        .name("host")
+        .invariant_unwrap("Capture group `host` always present")
+        .as_str();
+
+      let port_text = captures
+        .name("port")
+        .invariant_unwrap("Capture group `port` always present")
+        .as_str();
 
       let host = Host::parse(&host_text).context(host_port_parse_error::Host {
         text: text.to_owned(),

src/invariant.rs

@@ -0,0 +1,22 @@
+use crate::common::*;
+
+pub(crate) trait Invariant<T: Sized>: Sized {
+  fn invariant<D: Display>(self, invariant: D) -> Result<T>;
+
+  fn invariant_unwrap<D: Display>(self, invariant: D) -> T {
+    #![allow(clippy::result_unwrap_used)]
+    self.invariant(invariant).unwrap()
+  }
+}
+
+impl<T> Invariant<T> for Option<T> {
+  fn invariant<D: Display>(self, invariant: D) -> Result<T> {
+    self.ok_or_else(|| Error::internal(format!("Invariant violated: {}", invariant)))
+  }
+}
+
+impl<T, E: std::error::Error> Invariant<T> for Result<T, E> {
+  fn invariant<D: Display>(self, invariant: D) -> Result<T> {
+    self.map_err(|err| Error::internal(format!("Invariant `{}` violated: {}", invariant, err)))
+  }
+}

src/magnet_link.rs

@@ -50,7 +50,7 @@ impl MagnetLink {
   }
 
   pub(crate) fn to_url(&self) -> Url {
-    let mut url = Url::parse("magnet:").unwrap();
+    let mut url = Url::parse("magnet:").invariant_unwrap("`magnet:` is valid URL");
 
     let mut query = format!("xt=urn:btih:{}", self.infohash);
 

src/main.rs

@@ -13,9 +13,6 @@
   clippy::needless_pass_by_value,
   clippy::non_ascii_literal,
   clippy::option_map_unwrap_or_else,
-  clippy::option_unwrap_used,
-  clippy::result_expect_used,
-  clippy::result_unwrap_used,
   clippy::shadow_reuse,
   clippy::too_many_lines,
   clippy::unseparated_literal_suffix,
@@ -71,6 +68,7 @@ mod input_stream;
 mod input_target;
 mod into_u64;
 mod into_usize;
+mod invariant;
 mod lint;
 mod linter;
 mod magnet_link;

src/piece_list.rs

@@ -67,7 +67,13 @@ impl<'de> Deserialize<'de> for PieceList {
 
     let piece_hashes = bytes
       .chunks_exact(Sha1Digest::LENGTH)
-      .map(|chunk| Sha1Digest::from_bytes(chunk.try_into().unwrap()))
+      .map(|chunk| {
+        Sha1Digest::from_bytes(
+          chunk
+            .try_into()
+            .invariant_unwrap("chunks are all Sha1Digest::LENGTH"),
+        )
+      })
       .collect();
 
     Ok(Self { piece_hashes })

src/platform.rs

@@ -23,7 +23,12 @@ impl PlatformInterface for Platform {
 
     let mut stat: libc::stat = unsafe { mem::zeroed() };
 
-    let cpath = CString::new(path.as_os_str().as_bytes()).expect("Path contained null character.");
+    let cpath = if let Ok(cstr) = CString::new(path.as_os_str().as_bytes()) {
+      cstr
+    } else {
+      // Consider paths containing null bytes to be hidden
+      return Ok(true);
+    };
 
     let error_code = unsafe { libc::stat(cpath.as_ptr(), &mut stat) };
 

src/subcommand/torrent/stats.rs

@@ -128,7 +128,7 @@ struct Extractor {
 impl Extractor {
   fn new(print: bool, regexes: &[Regex]) -> Self {
     let regex_set = RegexSet::new(regexes.iter().map(Regex::as_str))
-      .expect("Validated regex pattern failed to recompile in regex set");
+      .invariant_unwrap("Regexes already validated by compilation");
 
     Self {
       bencode_decode_errors: 0,

src/subcommand/torrent/verify.rs

@@ -47,7 +47,7 @@ impl Verify {
       content.clone()
     } else {
       match &self.metainfo {
-        InputTarget::Path(path) => path.parent().unwrap().join(&metainfo.info.name),
+        InputTarget::Path(path) => path.join("..").join(&metainfo.info.name).clean(),
         InputTarget::Stdin => PathBuf::from(&metainfo.info.name),
       }
     };

src/torrent_summary.rs

@@ -62,7 +62,7 @@ impl TorrentSummary {
           creation_date
             .min(i64::max_value() as u64)
             .try_into()
-            .unwrap(),
+            .invariant_unwrap("min with i64 is always valid i64"),
           0,
         ),
       );

src/verifier.rs

@@ -79,7 +79,7 @@ impl<'a> Verifier<'a> {
       let to_buffer: usize = remaining
         .min(self.buffer.len().into_u64())
         .try_into()
-        .unwrap();
+        .invariant_unwrap("min with usize should fit in usize");
 
       let buffer = &mut self.buffer[0..to_buffer];