templates check: Add --stabilise flag to make renders reproducible

crates/cli/src/commands/server.rs

@@ -166,6 +166,8 @@ impl Options {
             &url_builder,
             // Don't use strict mode in production yet
             false,
+            // Don't stabilise in production
+            false,
         )
         .await?;
         shutdown.register_reloadable(&templates);

crates/cli/src/commands/templates.rs

@@ -8,6 +8,7 @@ use std::{fmt::Write, process::ExitCode};
 
 use anyhow::{Context as _, bail};
 use camino::Utf8PathBuf;
+use chrono::DateTime;
 use clap::Parser;
 use figment::Figment;
 use mas_config::{
@@ -34,14 +35,20 @@ enum Subcommand {
         /// The directory must either not exist or be empty.
         #[arg(long = "out-dir")]
         out_dir: Option<Utf8PathBuf>,
+
+        /// Attempt to remove 'unstable' template input data such as asset
+        /// hashes, in order to make renders more reproducible between
+        /// versions.
+        #[arg(long = "stabilise")]
+        stabilise: bool,
     },
 }
 
 impl Options {
     pub async fn run(self, figment: &Figment) -> anyhow::Result<ExitCode> {
         use Subcommand as SC;
         match self.subcommand {
-            SC::Check { out_dir } => {
+            SC::Check { out_dir, stabilise } => {
                 let _span = info_span!("cli.templates.check").entered();
 
                 let template_config = TemplatesConfig::extract_or_default(figment)
@@ -59,9 +66,17 @@ impl Options {
                 let captcha_config = CaptchaConfig::extract_or_default(figment)
                     .map_err(anyhow::Error::from_boxed)?;
 
-                let clock = SystemClock::default();
-                // XXX: we should disallow SeedableRng::from_entropy
-                let mut rng = rand_chacha::ChaChaRng::from_entropy();
+                let now = if stabilise {
+                    DateTime::from_timestamp_secs(0).unwrap()
+                } else {
+                    SystemClock::default().now()
+                };
+                let rng = if stabilise {
+                    rand_chacha::ChaChaRng::from_seed([42; 32])
+                } else {
+                    // XXX: we should disallow SeedableRng::from_entropy
+                    rand_chacha::ChaChaRng::from_entropy()
+                };
                 let url_builder =
                     mas_router::UrlBuilder::new("https://example.com/".parse()?, None, None);
                 let site_config = site_config_from_config(
@@ -75,11 +90,13 @@ impl Options {
                 let templates = templates_from_config(
                     &template_config,
                     &site_config,
-                    &url_builder, // Use strict mode in template checks
+                    &url_builder,
+                    // Use strict mode in template checks
                     true,
+                    stabilise,
                 )
                 .await?;
-                let all_renders = templates.check_render(clock.now(), &mut rng)?;
+                let all_renders = templates.check_render(now, &rng)?;
 
                 if let Some(out_dir) = out_dir {
                     // Save renders to disk.

crates/cli/src/commands/worker.rs

@@ -58,6 +58,8 @@ impl Options {
             &url_builder,
             // Don't use strict mode on task workers for now
             false,
+            // Don't stabilise in production
+            false,
         )
         .await?;
 

crates/cli/src/util.rs

@@ -233,11 +233,12 @@ pub async fn templates_from_config(
     site_config: &SiteConfig,
     url_builder: &UrlBuilder,
     strict: bool,
+    stabilise: bool,
 ) -> Result<Templates, anyhow::Error> {
     Templates::load(
         config.path.clone(),
         url_builder.clone(),
-        config.assets_manifest.clone(),
+        (!stabilise).then(|| config.assets_manifest.clone()),
         config.translations_path.clone(),
         site_config.templates_branding(),
         site_config.templates_features(),

crates/handlers/src/test_utils.rs

@@ -172,7 +172,7 @@ impl TestState {
         let templates = Templates::load(
             workspace_root.join("templates"),
             url_builder.clone(),
-            workspace_root.join("frontend/dist/manifest.json"),
+            Some(workspace_root.join("frontend/dist/manifest.json")),
             workspace_root.join("translations"),
             site_config.templates_branding(),
             site_config.templates_features(),

crates/spa/src/vite.rs

@@ -47,6 +47,48 @@ pub struct Manifest {
     inner: HashMap<Utf8PathBuf, ManifestEntry>,
 }
 
+impl Manifest {
+    /// Produce a sample manifest for use in reproducible sample renders.
+    #[must_use]
+    #[allow(clippy::missing_panics_doc)]
+    pub fn sample() -> Self {
+        let mut inner = HashMap::new();
+
+        for name in &[
+            "src/shared.css",
+            "src/templates.css",
+            "src/main.tsx",
+            "src/swagger.ts",
+        ] {
+            inner.insert(
+                name.parse().unwrap(),
+                ManifestEntry {
+                    name: None,
+                    names: None,
+                    src: None,
+                    // Construct a fake but slightly plausible dummy asset name.
+                    file: name
+                        .replace('/', "__")
+                        .replace('.', "-XXXXX.")
+                        .replace(".tsx", ".js")
+                        .replace(".ts", ".js")
+                        .parse()
+                        .unwrap(),
+                    css: None,
+                    assets: None,
+                    is_entry: None,
+                    is_dynamic_entry: None,
+                    imports: None,
+                    dynamic_imports: None,
+                    integrity: None,
+                },
+            );
+        }
+
+        Manifest { inner }
+    }
+}
+
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
 enum FileType {
     Script,

crates/templates/Cargo.toml

@@ -42,3 +42,6 @@ mas-i18n.workspace = true
 mas-iana.workspace = true
 mas-router.workspace = true
 mas-spa.workspace = true
+
+[dev-dependencies]
+rand_chacha.workspace = true