From 8a143c2b96291bf493152381ea90f103a78cfd3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Gr=C3=B6nke?= <stefan@gronke.net>
Date: Sun, 19 Jul 2026 18:58:02 +0000
Subject: [PATCH] feat: resolve xsl:import and xsl:include through a pluggable
 resolver

Imports and includes load through a StylesheetResolver, so a caller can supply stylesheet source from memory instead of the filesystem.
The filesystem stays the default via FileSystemResolver, and an InMemoryResolver reads from a map keyed by href.
xsl:import and xsl:include then resolve on targets without a filesystem, such as wasm32.

Refs #5
---
 xee-xslt-compiler/src/ast_ir.rs      | 79 ++++++++++++++--------------
 xee-xslt-compiler/src/lib.rs         |  9 +++-
 xee-xslt-compiler/src/resolver.rs    | 65 +++++++++++++++++++++++
 xee-xslt-compiler/src/run.rs         | 20 ++++++-
 xee-xslt-compiler/tests/test_xslt.rs | 72 ++++++++++++++++++++++++-
 5 files changed, 201 insertions(+), 44 deletions(-)
 create mode 100644 xee-xslt-compiler/src/resolver.rs

diff --git a/xee-xslt-compiler/src/ast_ir.rs b/xee-xslt-compiler/src/ast_ir.rs
index e2eec59aa..b84240dbb 100644
--- a/xee-xslt-compiler/src/ast_ir.rs
+++ b/xee-xslt-compiler/src/ast_ir.rs
@@ -2,7 +2,6 @@ use ahash::{HashMap, HashMapExt, HashSetExt};
 use xee_name::{Name, Namespaces, FN_NAMESPACE};
 
 use std::collections::HashSet;
-use std::path::PathBuf;
 use xee_interpreter::{
     context::StaticContext,
     error,
@@ -19,6 +18,7 @@ use xee_xslt_ast::{
 use xot::xmlname::{NameStrInfo, OwnedName};
 
 use crate::priority::default_priority;
+use crate::resolver::{FileSystemResolver, StylesheetResolver};
 
 struct IrConverter<'a> {
     variables: Variables,
@@ -69,6 +69,24 @@ pub fn parse_with_base_dir_and_initial_mode(
     xslt: &str,
     base_dir: Option<std::path::PathBuf>,
     initial_mode: Option<String>,
+) -> error::SpannedResult<interpreter::Program> {
+    let resolver = FileSystemResolver::new(base_dir);
+    parse_with_resolver_and_initial_mode(static_context, xslt, &resolver, initial_mode)
+}
+
+pub fn parse_with_resolver(
+    static_context: StaticContext,
+    xslt: &str,
+    resolver: &dyn StylesheetResolver,
+) -> error::SpannedResult<interpreter::Program> {
+    parse_with_resolver_and_initial_mode(static_context, xslt, resolver, None)
+}
+
+pub fn parse_with_resolver_and_initial_mode(
+    static_context: StaticContext,
+    xslt: &str,
+    resolver: &dyn StylesheetResolver,
+    initial_mode: Option<String>,
 ) -> error::SpannedResult<interpreter::Program> {
     let transform = parse_transform(xslt);
     // TODO: better error handling
@@ -82,7 +100,7 @@ pub fn parse_with_base_dir_and_initial_mode(
     // Process xsl:import and xsl:include directives
     let mut visited = HashSet::new();
     transform.declarations =
-        process_imports_and_includes(transform.declarations, base_dir, &mut visited)?;
+        process_imports_and_includes(transform.declarations, resolver, &mut visited)?;
 
     let initial_mode = parse_initial_mode_value(initial_mode)?;
     if matches!(initial_mode, ast::ApplyTemplatesModeValue::Unnamed) {
@@ -163,8 +181,8 @@ fn map_parse_error(xslt: &str, error: ElementError) -> error::SpannedError {
 
 fn process_imports_and_includes(
     declarations: ast::Declarations,
-    base_dir: Option<std::path::PathBuf>,
-    visited: &mut HashSet<PathBuf>,
+    resolver: &dyn StylesheetResolver,
+    visited: &mut HashSet<String>,
 ) -> error::SpannedResult<ast::Declarations> {
     let mut local_declarations = Vec::new();
     let mut imports = Vec::new(); // Collect imports in order
@@ -173,36 +191,34 @@ fn process_imports_and_includes(
         match &decl {
             ast::Declaration::Import(import) => {
                 // Load and parse the imported stylesheet
-                let (imported_decls, resolved_path) =
-                    load_stylesheet(&import.href.to_string(), base_dir.as_ref())?;
-                if visited.contains(&resolved_path) {
+                let (imported_decls, resolved_key) =
+                    load_stylesheet(&import.href.to_string(), resolver)?;
+                if visited.contains(&resolved_key) {
                     return Err(error::Error::Unsupported(format!(
                         "Circular import detected: '{}'",
-                        resolved_path.display()
+                        resolved_key
                     ))
                     .into());
                 }
-                visited.insert(resolved_path);
+                visited.insert(resolved_key);
                 // Recursively process imports in the imported stylesheet
-                let processed =
-                    process_imports_and_includes(imported_decls, base_dir.clone(), visited)?;
+                let processed = process_imports_and_includes(imported_decls, resolver, visited)?;
                 imports.push(processed);
             }
             ast::Declaration::Include(include) => {
                 // Load and parse the included stylesheet
-                let (included_decls, resolved_path) =
-                    load_stylesheet(&include.href.to_string(), base_dir.as_ref())?;
-                if visited.contains(&resolved_path) {
+                let (included_decls, resolved_key) =
+                    load_stylesheet(&include.href.to_string(), resolver)?;
+                if visited.contains(&resolved_key) {
                     return Err(error::Error::Unsupported(format!(
                         "Circular include detected: '{}'",
-                        resolved_path.display()
+                        resolved_key
                     ))
                     .into());
                 }
-                visited.insert(resolved_path);
+                visited.insert(resolved_key);
                 // Recursively process imports in the included stylesheet
-                let processed =
-                    process_imports_and_includes(included_decls, base_dir.clone(), visited)?;
+                let processed = process_imports_and_includes(included_decls, resolver, visited)?;
                 local_declarations.extend(processed);
             }
             _ => {
@@ -223,36 +239,19 @@ fn process_imports_and_includes(
 
 fn load_stylesheet(
     href: &str,
-    base_dir: Option<&std::path::PathBuf>,
-) -> error::SpannedResult<(ast::Declarations, PathBuf)> {
-    // Resolve the file path
-    let path = if let Some(base_dir) = base_dir {
-        base_dir.join(href)
-    } else {
-        std::path::PathBuf::from(href)
-    };
-
-    let canonical = path.canonicalize().unwrap_or_else(|_| path.clone());
-
-    // Try to read the file
-    let content = std::fs::read_to_string(&path).map_err(|e| {
-        error::Error::Unsupported(format!(
-            "Failed to load stylesheet '{}': {}",
-            path.display(),
-            e
-        ))
-    })?;
+    resolver: &dyn StylesheetResolver,
+) -> error::SpannedResult<(ast::Declarations, String)> {
+    let (content, key) = resolver.resolve(href)?;
 
     // Parse the stylesheet
     let transform = parse_transform(&content).map_err(|e| {
         error::Error::Unsupported(format!(
             "Failed to parse imported stylesheet '{}': {:?}",
-            path.display(),
-            e
+            href, e
         ))
     })?;
 
-    Ok((transform.declarations, canonical))
+    Ok((transform.declarations, key))
 }
 
 impl<'a> IrConverter<'a> {
diff --git a/xee-xslt-compiler/src/lib.rs b/xee-xslt-compiler/src/lib.rs
index 3451e8417..60605fc03 100644
--- a/xee-xslt-compiler/src/lib.rs
+++ b/xee-xslt-compiler/src/lib.rs
@@ -1,6 +1,11 @@
 mod ast_ir;
 mod priority;
+mod resolver;
 mod run;
 
-pub use ast_ir::{parse, parse_with_base_dir, parse_with_base_dir_and_initial_mode};
-pub use run::evaluate;
+pub use ast_ir::{
+    parse, parse_with_base_dir, parse_with_base_dir_and_initial_mode, parse_with_resolver,
+    parse_with_resolver_and_initial_mode,
+};
+pub use resolver::{FileSystemResolver, InMemoryResolver, StylesheetResolver};
+pub use run::{evaluate, evaluate_program, evaluate_with_resolver};
diff --git a/xee-xslt-compiler/src/resolver.rs b/xee-xslt-compiler/src/resolver.rs
new file mode 100644
index 000000000..c6d76821d
--- /dev/null
+++ b/xee-xslt-compiler/src/resolver.rs
@@ -0,0 +1,65 @@
+use std::collections::HashMap;
+use std::path::PathBuf;
+
+use xee_interpreter::error;
+
+/// Resolves an `xsl:import` or `xsl:include` `href` to stylesheet source.
+///
+/// The returned key canonically identifies the resolved stylesheet and is used
+/// to detect import cycles.
+pub trait StylesheetResolver {
+    fn resolve(&self, href: &str) -> error::SpannedResult<(String, String)>;
+}
+
+/// Reads imported stylesheets from the filesystem, resolving each `href` against
+/// an optional base directory.
+pub struct FileSystemResolver {
+    base_dir: Option<PathBuf>,
+}
+
+impl FileSystemResolver {
+    pub fn new(base_dir: Option<PathBuf>) -> Self {
+        Self { base_dir }
+    }
+}
+
+impl StylesheetResolver for FileSystemResolver {
+    fn resolve(&self, href: &str) -> error::SpannedResult<(String, String)> {
+        let path = match &self.base_dir {
+            Some(base_dir) => base_dir.join(href),
+            None => PathBuf::from(href),
+        };
+        let canonical = path.canonicalize().unwrap_or_else(|_| path.clone());
+        let content = std::fs::read_to_string(&path).map_err(|e| {
+            error::Error::Unsupported(format!(
+                "Failed to load stylesheet '{}': {}",
+                path.display(),
+                e
+            ))
+        })?;
+        Ok((content, canonical.to_string_lossy().into_owned()))
+    }
+}
+
+/// Resolves imported stylesheets from an in-memory map keyed by `href`, so
+/// `xsl:import` and `xsl:include` work without a filesystem.
+pub struct InMemoryResolver {
+    sources: HashMap<String, String>,
+}
+
+impl InMemoryResolver {
+    pub fn new(sources: HashMap<String, String>) -> Self {
+        Self { sources }
+    }
+}
+
+impl StylesheetResolver for InMemoryResolver {
+    fn resolve(&self, href: &str) -> error::SpannedResult<(String, String)> {
+        self.sources
+            .get(href)
+            .map(|source| (source.clone(), href.to_string()))
+            .ok_or_else(|| {
+                error::Error::Unsupported(format!("Stylesheet not found: '{}'", href)).into()
+            })
+    }
+}
diff --git a/xee-xslt-compiler/src/run.rs b/xee-xslt-compiler/src/run.rs
index 3361090f4..ed8911228 100644
--- a/xee-xslt-compiler/src/run.rs
+++ b/xee-xslt-compiler/src/run.rs
@@ -6,7 +6,8 @@ use xee_interpreter::error;
 use xee_interpreter::interpreter::Program;
 use xee_interpreter::sequence;
 
-use crate::ast_ir::parse;
+use crate::ast_ir::{parse, parse_with_resolver};
+use crate::resolver::StylesheetResolver;
 
 pub fn evaluate_program(
     xot: &mut Xot,
@@ -35,3 +36,20 @@ pub fn evaluate(xot: &mut Xot, xml: &str, xslt: &str) -> error::SpannedResult<se
     let program = parse(static_context, xslt).unwrap();
     evaluate_program(xot, &program, root)
 }
+
+pub fn evaluate_with_resolver(
+    xot: &mut Xot,
+    xml: &str,
+    xslt: &str,
+    resolver: &dyn StylesheetResolver,
+) -> error::SpannedResult<sequence::Sequence> {
+    let namespaces = Namespaces::new(
+        Namespaces::default_namespaces(),
+        "".to_string(),
+        FN_NAMESPACE.to_string(),
+    );
+    let static_context = StaticContext::from_namespaces(namespaces);
+    let root = xot.parse(xml).unwrap();
+    let program = parse_with_resolver(static_context, xslt, resolver)?;
+    evaluate_program(xot, &program, root)
+}
diff --git a/xee-xslt-compiler/tests/test_xslt.rs b/xee-xslt-compiler/tests/test_xslt.rs
index ddf3ec531..e7d2ac964 100644
--- a/xee-xslt-compiler/tests/test_xslt.rs
+++ b/xee-xslt-compiler/tests/test_xslt.rs
@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::fmt::Write;
 use std::fs;
 use std::time::{SystemTime, UNIX_EPOCH};
@@ -9,7 +10,9 @@ use xee_interpreter::{
     xml::Documents,
 };
 use xee_name::{Namespaces, FN_NAMESPACE};
-use xee_xslt_compiler::{evaluate, parse, parse_with_base_dir};
+use xee_xslt_compiler::{
+    evaluate, evaluate_with_resolver, parse, parse_with_base_dir, InMemoryResolver,
+};
 use xot::Xot;
 
 fn xml(xot: &Xot, sequence: Sequence) -> String {
@@ -2330,3 +2333,70 @@ fn test_basic_iterate_params() {
         "<o><baz>1</baz><baz>2</baz><baz>4</baz></o>"
     );
 }
+
+fn base_stylesheet(marker: &str) -> String {
+    format!(
+        r#"<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3">
+  <xsl:template match="/"><{marker}/></xsl:template>
+</xsl:transform>"#
+    )
+}
+
+#[test]
+fn test_import_from_memory() {
+    let mut xot = Xot::new();
+    let mut sources = HashMap::new();
+    sources.insert("base.xsl".to_string(), base_stylesheet("imported"));
+    let resolver = InMemoryResolver::new(sources);
+    let output = evaluate_with_resolver(
+        &mut xot,
+        "<doc/>",
+        r#"
+<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3">
+  <xsl:import href="base.xsl"/>
+</xsl:transform>"#,
+        &resolver,
+    )
+    .unwrap();
+    assert_eq!(xml(&xot, output), "<imported/>");
+}
+
+#[test]
+fn test_include_from_memory() {
+    let mut xot = Xot::new();
+    let mut sources = HashMap::new();
+    sources.insert("base.xsl".to_string(), base_stylesheet("included"));
+    let resolver = InMemoryResolver::new(sources);
+    let output = evaluate_with_resolver(
+        &mut xot,
+        "<doc/>",
+        r#"
+<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3">
+  <xsl:include href="base.xsl"/>
+</xsl:transform>"#,
+        &resolver,
+    )
+    .unwrap();
+    assert_eq!(xml(&xot, output), "<included/>");
+}
+
+#[test]
+fn test_import_precedence_from_memory() {
+    // The importing stylesheet outranks the imported one.
+    let mut xot = Xot::new();
+    let mut sources = HashMap::new();
+    sources.insert("base.xsl".to_string(), base_stylesheet("imported"));
+    let resolver = InMemoryResolver::new(sources);
+    let output = evaluate_with_resolver(
+        &mut xot,
+        "<doc/>",
+        r#"
+<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3">
+  <xsl:import href="base.xsl"/>
+  <xsl:template match="/"><main/></xsl:template>
+</xsl:transform>"#,
+        &resolver,
+    )
+    .unwrap();
+    assert_eq!(xml(&xot, output), "<main/>");
+}