Use serde instead of writing it out by hand

As a side benefit, this has much less copying.

metadata/Cargo.toml

@@ -13,5 +13,6 @@ description = "Document crates the same way docs.rs would"
 path = "lib.rs"
 
 [dependencies]
+serde = { version = "1.0", features = ["derive"] }
 toml = { version = "0.5", default-features = false }
 thiserror = "1"

metadata/lib.rs

@@ -8,7 +8,7 @@
 //! ```
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
 //! use std::process::Command;
-//! use metadata::Metadata;
+//! use docsrs_metadata::Metadata;
 //!
 //! // First, we need to parse Cargo.toml.
 //! let source_root = env!("CARGO_MANIFEST_DIR");
@@ -36,8 +36,9 @@ use std::collections::{HashMap, HashSet};
 use std::io;
 use std::path::Path;
 
+use serde::Deserialize;
 use thiserror::Error;
-use toml::{map::Map, Value};
+use toml::Value;
 
 /// The target that `metadata` is being built for.
 ///
@@ -91,19 +92,23 @@ pub enum MetadataError {
 /// ```
 ///
 /// You can define one or more fields in your `Cargo.toml`.
+#[derive(Deserialize)]
+#[serde(rename_all = "kebab-case")]
 pub struct Metadata {
     /// List of features to pass on to `cargo`.
     ///
     /// By default, docs.rs will only build default features.
     pub features: Option<Vec<String>>,
 
     /// Whether to pass `--all-features` to `cargo`.
+    #[serde(default)]
     pub all_features: bool,
 
     /// Whether to pass `--no-default-features` to `cargo`.
     //
     /// By default, Docs.rs will build default features.
-    /// Set `no-default-fatures` to `false` if you want to build only certain features.
+    /// Set `no-default-fatures` to `true` if you want to build only certain features.
+    #[serde(default)]
     pub no_default_features: bool,
 
     /// See [`BuildTargets`].
@@ -251,63 +256,31 @@ impl std::str::FromStr for Metadata {
 
     /// Parse the given manifest as TOML.
     fn from_str(manifest: &str) -> Result<Metadata, Self::Err> {
-        let mut metadata = Metadata::default();
+        use toml::value::Table;
 
-        let manifest = manifest.parse::<Value>()?;
-
-        fn fetch_manifest_tables<'a>(manifest: &'a Value) -> Option<&'a Map<String, Value>> {
-            manifest
-                .get("package")?
-                .as_table()?
-                .get("metadata")?
-                .as_table()?
-                .get("docs")?
-                .as_table()?
-                .get("rs")?
-                .as_table()
-        }
+        let manifest = match manifest.parse::<Value>()? {
+            Value::Table(t) => Some(t),
+            _ => None,
+        };
 
-        if let Some(table) = fetch_manifest_tables(&manifest) {
-            // TODO: all this `to_owned` is inefficient, this should use explicit matches instead.
-            let collect_into_array =
-                |f: &Vec<Value>| f.iter().map(|v| v.as_str().map(|v| v.to_owned())).collect();
-
-            metadata.features = table
-                .get("features")
-                .and_then(|f| f.as_array())
-                .and_then(collect_into_array);
-
-            metadata.no_default_features = table
-                .get("no-default-features")
-                .and_then(|v| v.as_bool())
-                .unwrap_or(metadata.no_default_features);
-
-            metadata.all_features = table
-                .get("all-features")
-                .and_then(|v| v.as_bool())
-                .unwrap_or(metadata.all_features);
-
-            metadata.default_target = table
-                .get("default-target")
-                .and_then(|v| v.as_str())
-                .map(|v| v.to_owned());
-
-            metadata.targets = table
-                .get("targets")
-                .and_then(|f| f.as_array())
-                .and_then(collect_into_array);
-
-            metadata.rustc_args = table
-                .get("rustc-args")
-                .and_then(|f| f.as_array())
-                .and_then(collect_into_array);
-
-            metadata.rustdoc_args = table
-                .get("rustdoc-args")
-                .and_then(|f| f.as_array())
-                .and_then(collect_into_array);
+        fn table<'a>(mut manifest: Table, table_name: &str) -> Option<Table> {
+            match manifest.remove(table_name) {
+                Some(Value::Table(table)) => Some(table),
+                _ => None,
+            }
         }
 
+        let table = manifest
+            .and_then(|t| table(t, "package"))
+            .and_then(|t| table(t, "metadata"))
+            .and_then(|t| table(t, "docs"))
+            .and_then(|t| table(t, "rs"));
+        let metadata = if let Some(table) = table {
+            Value::Table(table).try_into()?
+        } else {
+            Metadata::default()
+        };
+
         Ok(metadata)
     }
 }