Add borrow support for filter arguments

.github/workflows/tests.yml

@@ -17,32 +17,34 @@ jobs:
       - name: Test
         run: make test
 
-  build-old-stable:
-    name: Build on 1.45.0
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v1
-      - uses: actions-rs/toolchain@v1
-        with:
-          toolchain: 1.45.0
-          profile: minimal
-          override: true
-      - name: Build
-        run: cargo build --features=unstable_machinery,builtins,source,json,urlencode,debug,internal_debug
-        working-directory: ./minijinja
-        env:
-          CARGO_NET_GIT_FETCH_WITH_CLI: "true"
-          CARGO_HTTP_MULTIPLEXING: "false"
+  ## Bugs in older Rust versions for some of our borrowing logic for filters
+  ## No longer makes supporting this Rust version possible
+  # build-old-stable:
+  #   name: Build on 1.45.0
+  #   runs-on: ubuntu-latest
+  #   steps:
+  #     - uses: actions/checkout@v1
+  #     - uses: actions-rs/toolchain@v1
+  #       with:
+  #         toolchain: 1.45.0
+  #         profile: minimal
+  #         override: true
+  #     - name: Build
+  #       run: cargo build --features=unstable_machinery,builtins,source,json,urlencode,debug,internal_debug
+  #       working-directory: ./minijinja
+  #       env:
+  #         CARGO_NET_GIT_FETCH_WITH_CLI: "true"
+  #         CARGO_HTTP_MULTIPLEXING: "false"
 
   test-stable:
-    name: Test on 1.56.1
+    name: Test on 1.61.0
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v1
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.56.1
+          toolchain: 1.61.0
           profile: minimal
           override: true
       - name: Test

README.md

@@ -5,7 +5,7 @@
 [![Build Status](https://github.com/mitsuhiko/minijinja/workflows/Tests/badge.svg?branch=main)](https://github.com/mitsuhiko/minijinja/actions?query=workflow%3ATests)
 [![License](https://img.shields.io/github/license/mitsuhiko/minijinja)](https://github.com/mitsuhiko/minijinja/blob/main/LICENSE)
 [![Crates.io](https://img.shields.io/crates/d/minijinja.svg)](https://crates.io/crates/minijinja)
-[![rustc 1.45.0](https://img.shields.io/badge/rust-1.45%2B-orange.svg)](https://img.shields.io/badge/rust-1.45%2B-orange.svg)
+[![rustc 1.61.0](https://img.shields.io/badge/rust-1.61%2B-orange.svg)](https://img.shields.io/badge/rust-1.61%2B-orange.svg)
 [![Documentation](https://docs.rs/minijinja/badge.svg)](https://docs.rs/minijinja)
 
 </div>
@@ -63,9 +63,12 @@ fn main() {
 
 ## Minimum Rust Version
 
-MiniJinja supports Rust versions down to 1.45 at the moment.  For the order
-preservation feature Rust 1.49 is required as it uses the indexmap dependency
-which no longer supports older Rust versions.
+MiniJinja's development version requires Rust 1.61 due to limitations with
+HRTBs in older Rust versions.
+
+MiniJinja 0.20 supports Rust versions down to 1.45.  It is possible to write
+code that is compatible with both 0.20 and newer versions of MiniJinja which
+should make it possible to defer the upgrade to later.
 
 ## Sponsor
 

examples/dynamic/src/main.rs

@@ -2,7 +2,7 @@
 use std::fmt;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
-use minijinja::value::{FunctionArgs, Object, Value};
+use minijinja::value::{from_args, Object, Value};
 use minijinja::{Environment, Error, State};
 
 #[derive(Debug)]
@@ -19,7 +19,8 @@ impl fmt::Display for Cycler {
 
 impl Object for Cycler {
     fn call(&self, _state: &State, args: &[Value]) -> Result<Value, Error> {
-        let _: () = FunctionArgs::from_values(args)?;
+        // we don't want any args
+        from_args(args)?;
         let idx = self.idx.fetch_add(1, Ordering::Relaxed);
         Ok(self.values[idx % self.values.len()].clone())
     }
@@ -44,7 +45,8 @@ impl fmt::Display for Magic {
 impl Object for Magic {
     fn call_method(&self, _state: &State, name: &str, args: &[Value]) -> Result<Value, Error> {
         if name == "make_class" {
-            let (tag,): (String,) = FunctionArgs::from_values(args)?;
+            // single string argument
+            let (tag,): (&str,) = from_args(args)?;
             Ok(Value::from(format!("magic-{}", tag)))
         } else {
             Err(Error::new(

minijinja/src/compiler/codegen.rs

@@ -412,7 +412,7 @@ impl<'source> CodeGenerator<'source> {
                 for arg in &f.args {
                     self.compile_expr(arg)?;
                 }
-                self.add(Instruction::BuildList(f.args.len()));
+                self.add(Instruction::BuildList(f.args.len() + 1));
                 self.add(Instruction::ApplyFilter(f.name));
             }
             ast::Expr::Test(f) => {

minijinja/src/defaults.rs

@@ -118,6 +118,7 @@ pub(crate) fn get_builtin_filters() -> BTreeMap<&'static str, filters::BoxedFilt
             rv.insert("urlencode", BoxedFilter::new(filters::urlencode));
         }
     }
+
     rv
 }
 
@@ -151,5 +152,6 @@ pub(crate) fn get_globals() -> BTreeMap<&'static str, Value> {
         rv.insert("dict", BoxedFunction::new(functions::dict).to_value());
         rv.insert("debug", BoxedFunction::new(functions::debug).to_value());
     }
+
     rv
 }

minijinja/src/environment.rs

@@ -361,10 +361,11 @@ impl<'source> Environment<'source> {
     /// Filter functions are functions that can be applied to values in
     /// templates.  For details about filters have a look at
     /// [`Filter`](crate::filters::Filter).
-    pub fn add_filter<F, V, Rv, Args>(&mut self, name: &'source str, f: F)
+    pub fn add_filter<F, Rv, Args>(&mut self, name: &'source str, f: F)
     where
-        F: filters::Filter<V, Rv, Args>,
-        V: for<'a> ArgType<'a>,
+        // the crazy bounds here exist to enable borrowing in closures
+        F: filters::Filter<Rv, Args>
+            + for<'a> filters::Filter<Rv, <Args as FunctionArgs<'a>>::Output>,
         Rv: FunctionResult,
         Args: for<'a> FunctionArgs<'a>,
     {
@@ -381,11 +382,13 @@ impl<'source> Environment<'source> {
     /// Test functions are similar to filters but perform a check on a value
     /// where the return value is always true or false.  For details about tests
     /// have a look at [`Test`](crate::tests::Test).
-    pub fn add_test<F, V, Rv, Args>(&mut self, name: &'source str, f: F)
+    pub fn add_test<F, Rv, V, Args>(&mut self, name: &'source str, f: F)
     where
-        V: for<'a> ArgType<'a>,
+        // the crazy bounds here exist to enable borrowing in closures
+        F: tests::Test<Rv, V, Args>
+            + for<'a> tests::Test<Rv, <V as ArgType<'a>>::Output, <Args as FunctionArgs<'a>>::Output>,
         Rv: tests::TestResult,
-        F: tests::Test<V, Rv, Args>,
+        V: for<'a> ArgType<'a>,
         Args: for<'a> FunctionArgs<'a>,
     {
         self.tests.insert(name, tests::BoxedTest::new(f));
@@ -400,10 +403,14 @@ impl<'source> Environment<'source> {
     ///
     /// For details about functions have a look at [`functions`].  Note that
     /// functions and other global variables share the same namespace.
+    /// For more details about functions have a look at
+    /// [`Function`](crate::functions::Function).
     pub fn add_function<F, Rv, Args>(&mut self, name: &'source str, f: F)
     where
+        // the crazy bounds here exist to enable borrowing in closures
+        F: functions::Function<Rv, Args>
+            + for<'a> functions::Function<Rv, <Args as FunctionArgs<'a>>::Output>,
         Rv: FunctionResult,
-        F: functions::Function<Rv, Args>,
         Args: for<'a> FunctionArgs<'a>,
     {
         self.add_global(name, functions::BoxedFunction::new(f).to_value());