feat(build): support building without --fetch enabled

This eliminates the reqwest dependency and the heavy TLS library and
such. Reduces the binary size by about a third.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>

Author: tycho

Cargo.toml

@@ -11,12 +11,16 @@ rust-version   = "1.88"
 name           = "gloam"
 path           = "src/main.rs"
 
+[features]
+default = ["fetch"]
+fetch   = ["dep:reqwest"]
+
 [dependencies]
 anyhow         = "1"
 clap           = { version = "4", features = ["derive"] }
 indexmap       = { version = "2", features = ["serde"] }
 minijinja      = "2"
-reqwest        = { version = "0.13", features = ["blocking", "rustls"], default-features = false }
+reqwest        = { version = "0.13", features = ["blocking", "rustls"], default-features = false, optional = true}
 roxmltree      = "0.21"
 serde          = { version = "1", features = ["derive"] }
 xxhash-rust    = { version = "0.8", features = ["xxh3"] }

src/cli.rs

@@ -67,6 +67,7 @@ pub struct Cli {
     pub quiet: bool,
 
     /// Fetch XML specs from Khronos remote URLs instead of bundled copies.
+    #[cfg(feature = "fetch")]
     #[arg(long)]
     pub fetch: bool,
 
@@ -99,6 +100,17 @@ impl Cli {
             .collect()
     }
 
+    pub fn use_fetch(&self) -> bool {
+        #[cfg(feature = "fetch")]
+        {
+            self.fetch
+        }
+        #[cfg(not(feature = "fetch"))]
+        {
+            false
+        }
+    }
+
     /// Parse the --extensions argument into an `ExtensionFilter`.
     pub fn extension_filter(&self) -> Result<ExtensionFilter> {
         let Some(ref spec) = self.extensions else {

src/fetch.rs

@@ -1,6 +1,9 @@
 //! XML and auxiliary header loading. Default mode uses compile-time-embedded
 //! bundled copies; `--fetch` downloads from remote Khronos URLs.
 
+// In case we built without features=fetch
+#![allow(dead_code, unused)]
+
 use anyhow::{Context, Result};
 
 use crate::bundled;
@@ -36,14 +39,15 @@ pub struct SpecSources {
 // ---------------------------------------------------------------------------
 
 pub fn load_spec(spec_name: &str, use_fetch: bool) -> Result<SpecSources> {
+    #[cfg(feature = "fetch")]
     if use_fetch {
-        fetch_spec(spec_name)
-    } else {
-        bundled_spec(spec_name)
+        return fetch_spec(spec_name);
     }
+    bundled_spec(spec_name)
 }
 
 pub fn load_auxiliary_header(path: &str, use_fetch: bool) -> Result<String> {
+    #[cfg(feature = "fetch")]
     if use_fetch {
         if let Some(url) = auxiliary_url(path) {
             return fetch_text(&url)
@@ -116,6 +120,7 @@ fn bundled_auxiliary(path: &str) -> Result<&'static str> {
 // Fetch mode
 // ---------------------------------------------------------------------------
 
+#[cfg(feature = "fetch")]
 fn fetch_spec(spec_name: &str) -> Result<SpecSources> {
     let primary_url = match spec_name {
         "gl" => format!("{}gl.xml", BASE_GL),
@@ -160,6 +165,7 @@ fn auxiliary_url(path: &str) -> Option<String> {
     }
 }
 
+#[cfg(feature = "fetch")]
 fn fetch_text(url: &str) -> Result<String> {
     let resp = reqwest::blocking::get(url)
         .with_context(|| format!("GET {}", url))?

src/main.rs

@@ -49,7 +49,7 @@ fn run() -> Result<()> {
                 eprintln!("gloam: generating C loader...");
             }
             for fs in &feature_sets {
-                generator::c::generate(fs, c_args, out, cli.fetch, &command_line)?;
+                generator::c::generate(fs, c_args, out, cli.use_fetch(), &command_line)?;
             }
         }
     }

src/resolve.rs

@@ -292,7 +292,7 @@ pub fn build_feature_sets(cli: &Cli) -> Result<Vec<FeatureSet>> {
                 .push(req);
         }
         for (spec_name, reqs) in &by_spec {
-            let sources = fetch::load_spec(spec_name, cli.fetch)?;
+            let sources = fetch::load_spec(spec_name, cli.use_fetch())?;
             let raw = parse::parse(&sources, spec_name)?;
             let fs = resolve_feature_set(
                 &raw,
@@ -309,7 +309,7 @@ pub fn build_feature_sets(cli: &Cli) -> Result<Vec<FeatureSet>> {
     } else {
         for req in &requests {
             let spec_name = req.spec_name();
-            let sources = fetch::load_spec(spec_name, cli.fetch)?;
+            let sources = fetch::load_spec(spec_name, cli.use_fetch())?;
             let raw = parse::parse(&sources, spec_name)?;
             let fs = resolve_feature_set(
                 &raw,