feat(build-templated-pages): remove unused tera dependencies

This involves toggling off Tera's default features so crates such as rand are not pulled in. The only thing I had to do was recreate the slugify filter, since that is used in a template.

tools/build-templated-pages/Cargo.toml

@@ -8,6 +8,7 @@ license = "MIT OR Apache-2.0"
 
 [dependencies]
 toml_edit = { version = "0.21", default-features = false, features = ["parse"] }
-tera = "1.15"
+tera = { version = "1.19", default-features = false }
 serde = { version = "1.0", features = ["derive"] }
 bitflags = "2.3"
+slug = "0.1"

tools/build-templated-pages/src/examples.rs

@@ -129,13 +129,17 @@ pub(crate) fn check(what_to_run: Command) {
 
         let mut context = Context::new();
         context.insert("all_examples", &examples_by_category);
-        Tera::new("docs-template/*.md.tpl")
-            .expect("error parsing template")
-            .render_to(
-                "EXAMPLE_README.md.tpl",
-                &context,
-                File::create("examples/README.md").expect("error creating file"),
-            )
-            .expect("error rendering template");
+
+        let mut tera = Tera::new("docs-template/*.md.tpl").expect("error parsing template");
+
+        // Instead of automatically registering all of Tera's builtins, we use the one we need.
+        tera.register_filter("slugify", crate::slugify::slugify);
+
+        tera.render_to(
+            "EXAMPLE_README.md.tpl",
+            &context,
+            File::create("examples/README.md").expect("error creating file"),
+        )
+        .expect("error rendering template");
     }
 }

tools/build-templated-pages/src/main.rs

@@ -2,6 +2,7 @@ use bitflags::bitflags;
 
 mod examples;
 mod features;
+mod slugify;
 
 bitflags! {
     #[derive(Clone, Copy, Debug, PartialEq, Eq)]

tools/build-templated-pages/src/slugify.rs

@@ -0,0 +1,10 @@
+use std::collections::HashMap;
+
+use tera::{to_value, try_get_value, Result, Value};
+
+// A copy-and-paste from Tera. It is the only builtin we use.
+// https://github.com/Keats/tera/blob/290889e61e9fda317f42f284e7a875342424d646/src/builtins/filters/string.rs#L240-L243
+pub(crate) fn slugify(value: &Value, _: &HashMap<String, Value>) -> Result<Value> {
+    let s = try_get_value!("slugify", "value", String, value);
+    Ok(to_value(slug::slugify(s)).unwrap())
+}