Use pretty-print to display the actual values of individual elements in match explanations.

Previously, the standard debug output (:?) would be used to format individual elements of a collection when building an explanation why a matcher matched or did not match an actual value. Since the standard debug formatter packs the whole output in one line, and individual elements can be complex, this can lead to assertion failure messages which are hard to read.

This changes the output formatter in most cases to use the pretty-print formatter (:#?), which adds newlines and indentation reflecting the data structure.

For now, this change does not touch the display of keys in the has_entry matcher. In most cases, keys should be simple enough that the one-line debug output suffices. Splitting such simple structures into multiple lines in that context may have the opposite of the intended effect.

PiperOrigin-RevId: 505620778

Author: hovinenb

googletest/src/matchers/each_matcher.rs

@@ -81,7 +81,7 @@ where
         if non_matching_elements.len() == 1 {
             let (idx, element, explanation) = non_matching_elements.remove(0);
             return MatchExplanation::create(format!(
-                "whose element #{idx} is {element:?}, {explanation}"
+                "whose element #{idx} is {element:#?}, {explanation}"
             ));
         }
 
@@ -92,7 +92,7 @@ where
             .join(", ");
         let element_explanations = non_matching_elements
             .iter()
-            .map(|&(_, element, ref explanation)| format!("{element:?}, {explanation}"))
+            .map(|&(_, element, ref explanation)| format!("{element:#?}, {explanation}"))
             .collect::<Vec<_>>()
             .join("\n");
         MatchExplanation::create(format!(
@@ -247,7 +247,10 @@ Actual: [
     [
         1,
     ],
-], whose element #0 is [1, 2], whose element #1 is 2, which isn't equal to 1
+], whose element #0 is [
+    1,
+    2,
+], whose element #1 is 2, which isn't equal to 1
 "
             )))
         )

googletest/src/matchers/elements_are_matcher.rs

@@ -91,7 +91,7 @@ pub mod internal {
                 .zip(self.elements)
                 .enumerate()
                 .filter(|&(_, (a, e))| matches!(e.matches(a), MatcherResult::DoesNotMatch))
-                .map(|(idx, (a, e))| format!("element #{} is {:?}, {}", idx, a, e.explain_match(a)))
+                .map(|(idx, (a, e))| format!("element #{idx} is {a:#?}, {}", e.explain_match(a)))
                 .collect::<Vec<_>>();
             if mismatches.is_empty() {
                 MatchExplanation::create("whose elements all match".to_string())

googletest/src/matchers/err_matcher.rs

@@ -42,7 +42,7 @@ impl<T: Debug, E: Debug, InnerMatcherT: Matcher<E>> Matcher<Result<T, E>>
     fn explain_match(&self, actual: &Result<T, E>) -> MatchExplanation {
         match actual {
             Err(e) => MatchExplanation::create(format!(
-                "which is an error containing {e:?}, {}",
+                "which is an error containing {e:#?}, {}",
                 self.inner.explain_match(e)
             )),
             Ok(_) => MatchExplanation::create("which is a success".to_string()),

googletest/src/matchers/has_entry_matcher.rs

@@ -66,7 +66,7 @@ impl<KeyT: Debug + Eq + Hash, ValueT: Debug, MatcherT: Matcher<ValueT>>
     fn explain_match(&self, actual: &HashMap<KeyT, ValueT>) -> MatchExplanation {
         if let Some(value) = actual.get(&self.key) {
             MatchExplanation::create(format!(
-                "which contains key {:?}, but is mapped to value {:?}, {}",
+                "which contains key {:?}, but is mapped to value {:#?}, {}",
                 self.key,
                 value,
                 self.inner.explain_match(value)

googletest/src/matchers/ok_matcher.rs

@@ -42,7 +42,7 @@ impl<T: Debug, E: Debug, InnerMatcherT: Matcher<T>> Matcher<Result<T, E>>
     fn explain_match(&self, actual: &Result<T, E>) -> MatchExplanation {
         match actual {
             Ok(o) => MatchExplanation::create(format!(
-                "which is a success containing {o:?}, {}",
+                "which is a success containing {o:#?}, {}",
                 self.inner.explain_match(o)
             )),
             Err(_) => MatchExplanation::create("which is an error".to_string()),

googletest/src/matchers/pointwise_matcher.rs

@@ -117,7 +117,7 @@ pub mod internal {
                 .zip(self.matchers.iter())
                 .enumerate()
                 .filter(|&(_, (a, e))| matches!(e.matches(a), MatcherResult::DoesNotMatch))
-                .map(|(idx, (a, e))| format!("element #{} is {:?}, {}", idx, a, e.explain_match(a)))
+                .map(|(idx, (a, e))| format!("element #{idx} is {a:#?}, {}", e.explain_match(a)))
                 .collect::<Vec<_>>();
             if mismatches.is_empty() {
                 MatchExplanation::create("which matches all elements".to_string())

googletest/src/matchers/some_matcher.rs

@@ -40,7 +40,7 @@ impl<T: Debug, InnerMatcherT: Matcher<T>> Matcher<Option<T>> for SomeMatcher<Inn
     fn explain_match(&self, actual: &Option<T>) -> MatchExplanation {
         match (self.matches(actual), actual) {
             (_, Some(t)) => MatchExplanation::create(format!(
-                "which contains {t:?}, {}",
+                "which contains {t:#?}, {}",
                 self.inner.explain_match(t)
             )),
             (_, None) => MatchExplanation::create("which is none".to_string()),

googletest/src/matchers/subset_of_matcher.rs

@@ -88,7 +88,7 @@ where
             .into_iter()
             .enumerate()
             .filter(|&(_, actual_item)| self.expected_is_missing(actual_item))
-            .map(|(idx, actual_item)| format!("{actual_item:?} at #{idx}"))
+            .map(|(idx, actual_item)| format!("{actual_item:#?} at #{idx}"))
             .collect::<Vec<_>>();
 
         match unexpected_elements.len() {
@@ -106,8 +106,8 @@ where
 
     fn describe(&self, matcher_result: MatcherResult) -> String {
         match matcher_result {
-            MatcherResult::Matches => format!("is a subset of {:?}", self.superset),
-            MatcherResult::DoesNotMatch => format!("isn't a subset of {:?}", self.superset),
+            MatcherResult::Matches => format!("is a subset of {:#?}", self.superset),
+            MatcherResult::DoesNotMatch => format!("isn't a subset of {:#?}", self.superset),
         }
     }
 }
@@ -195,7 +195,11 @@ mod tests {
             err(displays_as(contains_substring(
                 "\
 Value of: vec![0, 2, 3]
-Expected: is a subset of [1, 2, 3]
+Expected: is a subset of [
+    1,
+    2,
+    3,
+]
 Actual: [
     0,
     2,
@@ -215,7 +219,11 @@ Actual: [
             err(displays_as(contains_substring(
                 "\
 Value of: vec![1, 0, 3]
-Expected: is a subset of [1, 2, 3]
+Expected: is a subset of [
+    1,
+    2,
+    3,
+]
 Actual: [
     1,
     0,
@@ -235,7 +243,11 @@ Actual: [
             err(displays_as(contains_substring(
                 "\
 Value of: vec![0, 0, 3]
-Expected: is a subset of [1, 2, 3]
+Expected: is a subset of [
+    1,
+    2,
+    3,
+]
 Actual: [
     0,
     0,

googletest/src/matchers/superset_of_matcher.rs

@@ -88,7 +88,7 @@ where
             .subset
             .into_iter()
             .filter(|expected_item| actual_is_missing(actual, expected_item))
-            .map(|expected_item| format!("{expected_item:?}"))
+            .map(|expected_item| format!("{expected_item:#?}"))
             .collect();
         match missing_items.len() {
             0 => MatchExplanation::create("whose no element is missing".to_string()),
@@ -104,8 +104,8 @@ where
 
     fn describe(&self, matcher_result: MatcherResult) -> String {
         match matcher_result {
-            MatcherResult::Matches => format!("is a superset of {:?}", self.subset),
-            MatcherResult::DoesNotMatch => format!("isn't a superset of {:?}", self.subset),
+            MatcherResult::Matches => format!("is a superset of {:#?}", self.subset),
+            MatcherResult::DoesNotMatch => format!("isn't a superset of {:#?}", self.subset),
         }
     }
 }
@@ -194,7 +194,11 @@ mod tests {
             err(displays_as(contains_substring(
                 "\
 Value of: vec![0, 2, 3]
-Expected: is a superset of [1, 2, 3]
+Expected: is a superset of [
+    1,
+    2,
+    3,
+]
 Actual: [
     0,
     2,
@@ -214,7 +218,11 @@ Actual: [
             err(displays_as(contains_substring(
                 "\
 Value of: vec![1, 0, 3]
-Expected: is a superset of [1, 2, 3]
+Expected: is a superset of [
+    1,
+    2,
+    3,
+]
 Actual: [
     1,
     0,
@@ -234,7 +242,11 @@ Actual: [
             err(displays_as(contains_substring(
                 "\
 Value of: vec![0, 0, 3]
-Expected: is a superset of [1, 2, 3]
+Expected: is a superset of [
+    1,
+    2,
+    3,
+]
 Actual: [
     0,
     0,

googletest/src/matchers/unordered_elements_are_matcher.rs

@@ -692,7 +692,7 @@ pub mod internal {
             for (actual_idx, expected_idx) in self.get_matches() {
                 error_message.push_str(
                     format!(
-                        "\n    Actual element {:?} at index {actual_idx} matched expected element `{}` at index {expected_idx}.",
+                        "\n    Actual element {:#?} at index {actual_idx} matched expected element `{}` at index {expected_idx}.",
                         actual[actual_idx],
                         expected[expected_idx].describe(MatcherResult::Matches),
                     )
@@ -702,7 +702,7 @@ pub mod internal {
 
             for actual_idx in self.get_unmatched_actual() {
                 error_message.push_str(format!(
-                    "\n    Actual element {:?} at index {actual_idx} did not match any remaining expected element.",
+                    "\n    Actual element {:#?} at index {actual_idx} did not match any remaining expected element.",
                     actual[actual_idx]
                 ).as_str());
             }