Added rounded_redaction (#350)

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to insta and cargo-insta are documented here.
 - Added a way to disable diffing in review. (#348)
 - Added three argument version of `glob!` to set a different base
   path. (#347)
+- Added `rounded_redaction` to truncate floating point values.
 
 ## 1.27.0
 

src/lib.rs

@@ -304,7 +304,7 @@ pub mod _cargo_insta_support {
 
 // useful for redactions
 #[cfg(feature = "redactions")]
-pub use crate::redaction::{dynamic_redaction, sorted_redaction};
+pub use crate::redaction::{dynamic_redaction, rounded_redaction, sorted_redaction};
 
 // these are here to make the macros work
 #[doc(hidden)]

src/redaction.rs

@@ -166,6 +166,27 @@ pub fn sorted_redaction() -> Redaction {
     dynamic_redaction(sort)
 }
 
+/// Creates a redaction that rounds floating point numbers to a given
+/// number of decimal places.
+///
+/// ```rust
+/// # use insta::{Settings, rounded_redaction};
+/// # let mut settings = Settings::new();
+/// settings.add_redaction(".sum", rounded_redaction(2));
+/// ```
+#[cfg_attr(docsrs, doc(cfg(feature = "redactions")))]
+pub fn rounded_redaction(decimals: usize) -> Redaction {
+    dynamic_redaction(move |value: Content, _path: ContentPath| -> Content {
+        let f = match value.resolve_inner() {
+            Content::F32(f) => *f as f64,
+            Content::F64(f) => *f,
+            _ => return value,
+        };
+        let x = 10f64.powf(decimals as f64);
+        Content::F64((f * x).round() / x)
+    })
+}
+
 impl Redaction {
     /// Performs the redaction of the value at the given path.
     fn redact(&self, value: Content, path: &[PathItem]) -> Content {

tests/snapshots/test_redaction__rounded_redaction.snap

@@ -0,0 +1,8 @@
+---
+source: tests/test_redaction.rs
+expression: "&MyPoint { x: 1.0 / 3.0, y: 6.0 / 3.0 }"
+---
+{
+  "x": 0.3333,
+  "y": 2.0
+}

tests/test_redaction.rs

@@ -414,3 +414,25 @@ fn test_ordering_newtype_set() {
         }
     );
 }
+
+#[cfg(feature = "json")]
+#[test]
+fn test_rounded_redaction() {
+    #[derive(Debug, Serialize)]
+    pub struct MyPoint {
+        x: f64,
+        y: f64,
+    }
+
+    assert_json_snapshot!(
+        "rounded_redaction",
+        &MyPoint {
+            x: 1.0 / 3.0,
+            y: 6.0 / 3.0,
+        },
+        {
+            ".x" => insta::rounded_redaction(4),
+            ".y" => insta::rounded_redaction(4),
+        }
+    );
+}