Add test_path_filter and deprecate test_file_filter.

`test_file_filter` filters out non-file things, which makes it
impossible to, for example, use directories as tests.

Rather than change the semantics of `test_file_filter`, this commit adds
`test_path_filter` which doesn't filter out non-file things, but is
otherwise identical to `test_file_filter`. It also marks
`test_file_filter` as deprecated, with a generic way to migrate code to
`test_path_filter`, allowing users to mechanically migrate their code.

examples/fm_options/run_tests.rs

@@ -9,7 +9,7 @@ use regex::Regex;
 fn main() {
     LangTester::new()
         .test_dir("examples/fm_options/lang_tests")
-        .test_file_filter(|p| p.extension().unwrap().to_str().unwrap() == "py")
+        .test_path_filter(|p| p.extension().and_then(|x| x.to_str()) == Some("py"))
         .test_extract(|p| {
             read_to_string(p)
                 .unwrap()

examples/rust_lang_tester/run_tests.rs

@@ -18,7 +18,7 @@ fn main() {
     LangTester::new()
         .test_dir("examples/rust_lang_tester/lang_tests")
         // Only use files named `*.rs` as test files.
-        .test_file_filter(|p| p.extension().unwrap().to_str().unwrap() == "rs")
+        .test_path_filter(|p| p.extension().and_then(|x| x.to_str()) == Some("rs"))
         // Extract the first sequence of commented line(s) as the tests.
         .test_extract(|p| {
             read_to_string(p)

lang_tests/rerun/main.rs

@@ -34,7 +34,7 @@ fn main() {
     LangTester::new()
         .rerun_at_most(5)
         .test_dir("lang_tests/rerun/")
-        .test_file_filter(|p| p.extension().unwrap().to_str().unwrap() == "py")
+        .test_path_filter(|p| p.extension().and_then(|x| x.to_str()) == Some("py"))
         .test_extract(|p| {
             read_to_string(p)
                 .unwrap()

src/lib.rs

@@ -23,7 +23,7 @@
 //!     LangTester::new()
 //!         .test_dir("examples/rust_lang_tester/lang_tests")
 //!         // Only use files named `*.rs` as test files.
-//!         .test_file_filter(|p| p.extension().unwrap().to_str().unwrap() == "rs")
+//!         .test_path_filter(|p| p.extension().and_then(|x| x.to_str()) == Some("rs"))
 //!         // Extract the first sequence of commented line(s) as the tests.
 //!         .test_extract(|p| {
 //!             read_to_string(p)

src/tester.rs

@@ -49,7 +49,7 @@ const DEFAULT_RERUN_AT_MOST: u64 = 3;
 
 pub struct LangTester {
     use_cmdline_args: bool,
-    test_file_filter: Option<Box<dyn Fn(&Path) -> bool + RefUnwindSafe>>,
+    test_path_filter: Option<Box<dyn Fn(&Path) -> bool + RefUnwindSafe>>,
     cmdline_filters: Option<Vec<String>>,
     inner: Arc<LangTesterPooler>,
 }
@@ -87,7 +87,7 @@ impl LangTester {
     /// [`test_cmds`](#method.test_cmds).
     pub fn new() -> Self {
         LangTester {
-            test_file_filter: None,
+            test_path_filter: None,
             use_cmdline_args: true,
             cmdline_filters: None,
             inner: Arc::new(LangTesterPooler {
@@ -140,11 +140,35 @@ impl LangTester {
     /// ```
     ///
     /// Note that `lang_tester` recursively searches directories for files.
-    pub fn test_file_filter<F>(&mut self, test_file_filter: F) -> &mut Self
+    #[deprecated(
+        since = "0.7.5",
+        note = "Convert `test_file_filter(|p| ...)` to `test_path_fiter(|p| p.is_file() & ...)`"
+    )]
+    pub fn test_file_filter<F>(&mut self, test_path_filter: F) -> &mut Self
     where
         F: 'static + Fn(&Path) -> bool + RefUnwindSafe,
     {
-        self.test_file_filter = Some(Box::new(test_file_filter));
+        self.test_path_filter = Some(Box::new(move |p| p.is_file() && test_path_filter(p)));
+        self
+    }
+
+    /// If `test_path_filter` is specified, only paths for which it returns `true` will be
+    /// considered tests. A common use of this is to filter tests based on filename extensions
+    /// e.g.:
+    ///
+    /// ```rust,ignore
+    /// LangTester::new()
+    ///     ...
+    ///     .test_path_filter(|p| p.extension().and_then(|x| x.to_str()) == Some("rs"))
+    ///     ...
+    /// ```
+    ///
+    /// Note that `lang_tester` recursively searches directories.
+    pub fn test_path_filter<F>(&mut self, test_path_filter: F) -> &mut Self
+    where
+        F: 'static + Fn(&Path) -> bool + RefUnwindSafe,
+    {
+        self.test_path_filter = Some(Box::new(test_path_filter));
         self
     }
 
@@ -304,10 +328,9 @@ impl LangTester {
         let paths = WalkDir::new(self.inner.test_dir.as_ref().unwrap())
             .into_iter()
             .filter_map(|x| x.ok())
-            .filter(|x| x.file_type().is_file())
             .map(|x| canonicalize(x.into_path()).unwrap())
             // Filter out non-test files
-            .filter(|x| match self.test_file_filter.as_ref() {
+            .filter(|x| match self.test_path_filter.as_ref() {
                 Some(f) => match catch_unwind(|| f(x)) {
                     Ok(b) => b,
                     Err(_) => {