docs: overhaul readme and make sure everything is documented

Fixes: #15

Cargo.toml

@@ -19,7 +19,7 @@ atty = "0.2.14"
 ci_info = "0.14.2"
 
 [dev-dependencies]
-thiserror = "1.0.26"
+semver = "1.0.4"
 
 [workspace]
 members = ["miette-derive"]

README.md

@@ -3,10 +3,10 @@ coder! Error code for One Thousand Lines!
 
 ## About
 
-`miette` is a diagnostic library for Rust. It includes a series of protocols
-that allow you to hook into its error reporting facilities, and even write
-your own error reports! It lets you define error types that can print out like
-this (or in any format you like!):
+`miette` is a diagnostic library for Rust. It includes a series of
+traits/protocols that allow you to hook into its error reporting facilities,
+and even write your own error reports! It lets you define error types that can
+print out like this (or in any format you like!):
 
 <img src="https://raw.githubusercontent.com/zkat/miette/main/images/serde_json.png" alt="Hi! miette also includes a screen-reader-oriented diagnostic printer that's enabled in various situations, such as when you use NO_COLOR or CLICOLOR settings, or on CI. This behavior is also fully configurable and customizable. For example, this is what this particular diagnostic will look like when the narrated printer is enabled:
 \
@@ -24,21 +24,35 @@ but it's definitely a bug and should be reported.
 diagnostic error code: ruget::api::bad_json
 " />
 
-The [Diagnostic] trait in `miette` is an extension of `std::error::Error` that
-adds various facilities like [Severity], error codes that could be looked up
-by users, and snippet display with support for multiline reports, arbitrary
-[Source]s, and pretty printing.
+## Table of Contents <!-- omit in toc -->
 
-`miette` also includes a (lightweight) `anyhow`/`eyre`-style
-[DiagnosticReport] type which can be returned from application-internal
-functions to make the `?` experience nicer. It's extra easy to use when using
-[DiagnosticResult]!
+- [About](#about)
+- [Features](#features)
+- [Installing](#installing)
+- [Example](#example)
+- [Usage](#usage)
+  - [... in libraries](#-in-libraries)
+  - [... in application code](#-in-application-code)
+  - [... in `main()`](#-in-main)
+  - [... snippets](#-snippets)
+- [License](#license)
 
-While the `miette` crate bundles some baseline implementations for [Source]
-and [DiagnosticReportPrinter], it's intended to define a protocol that other crates
-can build on top of to provide rich error reporting, and encourage an
-ecosystem that leans on this extra metadata to provide it for others in a way
-that's compatible with [std::error::Error].
+## Features
+
+- Generic [Diagnostic] protocol, compatible (and dependent on) `std::error::Error`.
+- Unique error codes on every [Diagnostic].
+- Super handy derive macro for defining diagnostic metadata.
+- Lightweight [`anyhow`](https://docs.rs/anyhow)/[`eyre`](https://docs.rs/eyre)-style error wrapper type, [DiagnosticReport],
+  which can be returned from `main`.
+- Generic support for arbitrary [Source]s for snippet data, with default support for `String`s included.
+
+The `miette` crate also comes bundles with a default [DiagnosticReportPrinter] with the following features:
+
+- Fancy graphical [diagnostic output](#about), using ANSI/Unicode text
+- single- and multi-line highlighting support
+- Screen reader/braille support, gated on [`NO_COLOR`](http://no-color.org/), and other heuristics.
+- Fully customizable graphical theming (or overriding the printers entirely).
+- Cause chain printing
 
 ## Installing
 
@@ -48,7 +62,7 @@ Using [`cargo-edit`](https://crates.io/crates/cargo-edit):
 $ cargo add miette
 ```
 
-## Example and Guide
+## Example
 
 ```rust
 /*
@@ -82,8 +96,8 @@ Use this DiagnosticResult type (or its expanded version) as the return type
 throughout your app (but NOT your libraries! Those should always return concrete
 types!).
 */
-use miette::DiagnosticResult as Result;
-fn this_fails() -> Result<()> {
+use miette::DiagnosticResult;
+fn this_fails() -> DiagnosticResult<()> {
     // You can use plain strings as a `Source`, or anything that implements
     // the one-method `Source` trait.
     let src = "source\n  text\n    here".to_string();
@@ -99,12 +113,12 @@ fn this_fails() -> Result<()> {
 }
 
 /*
-Now to get everything printed nicely, just return a Result<(), DiagnosticReport>
+Now to get everything printed nicely, just return a DiagnosticResult<()>
 and you're all set!
 
 Note: You can swap out the default reporter for a custom one using `miette::set_reporter()`
 */
-fn pretend_this_is_main() -> Result<()> {
+fn pretend_this_is_main() -> DiagnosticResult<()> {
     // kaboom~
     this_fails()?;
 
@@ -131,6 +145,119 @@ diagnostic help: try doing it better next time?
 diagnostic error code: oops::my::bad
 ">
 
+## Usage
+
+### ... in libraries
+
+`miette` is _fully compatible_ with library usage. Consumers who don't know
+about, or don't want, `miette` features can safely use its error types as
+regular [std::error::Error].
+
+We highly recommend using something like [`thiserror`](https://docs.rs/thiserror) to define unique error types and error wrappers for your library.
+
+While `miette` integrates smoothly with `thiserror`, it is _not required_. If
+you don't want to use the [Diagnostic] derive macro, you can implement the
+trait directly, just like with `std::error::Error`.
+
+```rust
+// lib/error.rs
+use thiserror::Error;
+use miette::Diagnostic;
+
+#[derive(Error, Diagnostic, Debug)]
+pub enum MyLibError {
+    #[error(transparent)]
+    #[diagnostic(code(my_lib::io_error))]
+    IoError(#[from] std::io::Error),
+
+    #[error("Oops it blew up")]
+    #[diagnostic(code(my_lib::bad_code))]
+    BadThingHappened,
+}
+```
+
+Then, return this error type from all your fallible public APIs. It's a best
+practice to wrap any "external" error types in your error `enum` instead of
+using something like [eyre](https://docs.rs/eyre) in a library.
+
+### ... in application code
+
+Application code tends to work a little differently than libraries. You don't
+always need or care to define dedicated error wrappers for errors coming from
+external libraries and tools.
+
+For this situation, `miette` includes two tools: [DiagnosticReport] and
+[IntoDiagnostic]. They work in tandem to make it easy to convert regular
+`std::error::Error`s into [Diagnostic]s. Additionally, there's a
+[DiagnosticResult] type alias that you can use to be more terse:
+
+```rust
+// my_app/lib/my_internal_file.rs
+use miette::{IntoDiagnostic, DiagnosticResult};
+use semver::Version;
+
+pub fn some_tool() -> DiagnosticResult<Version> {
+    Ok("1.2.x".parse().into_diagnostic("my_app::semver::parse_error")?)
+}
+```
+
+### ... in `main()`
+
+`main()` is just like any other part of your application-internal code. Use
+`DiagnosticResult` as your return value, and it will pretty-print your
+diagnostics automatically.
+
+```rust
+use miette::{DiagnosticResult, IntoDiagnostic};
+use semver::Version;
+
+fn pretend_this_is_main() -> DiagnosticResult<()> {
+    let version: Version = "1.2.x".parse().into_diagnostic("my_app::semver::parse_error")?;
+    println!("{}", version);
+    Ok(())
+}
+```
+
+### ... snippets
+
+Along with its general error handling and reporting features, `miette` also
+includes facilities for adding error spans and annotations/highlights to your
+output. This can be very useful when an error is syntax-related, but you can
+even use it to print out sections of your own source code!
+
+To achieve this, `miette` defines its own lightweight [SourceSpan] type. This
+is a basic byte-offset and length into an associated [Source] and, along with
+the latter, gives `miette` all the information it needs to pretty-print some
+snippets!
+
+The easiest way to define errors like this is to use the `derive(Diagnostic)`
+macro:
+
+```rust
+use miette::{Diagnostic, SourceSpan};
+use thiserror::Error;
+
+#[derive(Diagnostic, Debug, Error)]
+#[error("oops")]
+#[diagnostic(code(my_lib::random_error))]
+pub struct MyErrorType {
+    // The `Source` that miette will use.
+    src: String,
+
+    // A snippet that points to `src`, our `Source`. The filename can be
+    // provided at the callsite.
+    #[snippet(src, "This is the snippet")]
+    snip: SourceSpan,
+
+    // A highlight for the `snip` snippet we defined above. This will
+    // underline/mark the specific code inside the larger snippet context.
+    //
+    // The label is provided using `SourceSpan`'s label.
+    #[highlight(snip)]
+    err_span: SourceSpan,
+}
+```
+
 ## License
 
 `miette` is released to the Rust community under the [Apache license 2.0](./LICENSE).

src/lib.rs

@@ -1,4 +1,7 @@
 #![doc = include_str!("../README.md")]
+#![deny(missing_docs)]
+// #![deny(missing_docs, missing_debug_implementations, nonstandard_style)]
+// #![warn(unreachable_pub, rust_2018_idioms)]
 
 pub use miette_derive::*;
 

src/printer/narratable_printer.rs

@@ -5,15 +5,16 @@ use crate::protocol::{Diagnostic, DiagnosticReportPrinter, DiagnosticSnippet, Se
 use crate::{SourceSpan, SpanContents};
 
 /**
-Reference implementation of the [DiagnosticReportPrinter] trait. This is generally
-good enough for simple use-cases, and is the default one installed with `miette`,
-but you might want to implement your own if you want custom reporting for your
-tool or app.
+[DiagnosticReportPrinter] that renders plain text and avoids extraneous graphics.
+It's optimized for screen readers and braille users, but is also used in any
+non-graphical environments, such as non-TTY output.
 */
 #[derive(Debug, Clone)]
 pub struct NarratableReportPrinter;
 
 impl NarratableReportPrinter {
+    /// Create a new [NarratableReportPrinter]. There are no customization
+    /// options.
     pub fn new() -> Self {
         Self
     }
@@ -26,6 +27,10 @@ impl Default for NarratableReportPrinter {
 }
 
 impl NarratableReportPrinter {
+    /// Render a [Diagnostic]. This function is mostly internal and meant to
+    /// be called by the toplevel [DiagnosticReportPrinter] handler, but is
+    /// made public to make it easier (possible) to test in isolation from
+    /// global state.
     pub fn render_report(
         &self,
         f: &mut impl fmt::Write,

src/protocol.rs

@@ -233,6 +233,7 @@ pub struct SourceSpan {
 }
 
 impl SourceSpan {
+    /// Create a new [SourceSpan].
     pub fn new(start: SourceOffset, length: SourceOffset) -> Self {
         Self {
             label: None,
@@ -241,6 +242,7 @@ impl SourceSpan {
         }
     }
 
+    /// Create a new [SourceSpan] with a label.
     pub fn new_labeled(label: impl AsRef<str>, start: SourceOffset, length: SourceOffset) -> Self {
         Self {
             label: Some(label.as_ref().into()),
@@ -249,18 +251,27 @@ impl SourceSpan {
         }
     }
 
+    /// The absolute offset, in bytes, from the beginning of a [Source].
     pub fn offset(&self) -> usize {
         self.offset.offset()
     }
 
+    /// Returns a reference to this [SourceSpan]'s label. This label may be
+    /// used for different things in different contexts. In highlights, it
+    /// will be interpreted as the text on the other end of an underscored
+    /// section of text. In snippet spans, this will be treated as the source
+    /// name.
     pub fn label(&self) -> Option<&str> {
         self.label.as_ref().map(|x| &x[..])
     }
 
+    /// Total length of the [SourceSpan], in bytes.
     pub fn len(&self) -> usize {
         self.length.offset()
     }
 
+    /// Whether this [SourceSpan] has a length of zero. It may still be useful
+    /// to point to a specific point.
     pub fn is_empty(&self) -> bool {
         self.length.offset() == 0
     }