1 // Copyright 2022 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 use crate::description::Description;
16 use crate::matcher::{Matcher, MatcherResult};
17 use std::fmt::{Debug, Display};
18 use std::marker::PhantomData;
19
20 /// Matches the string representation of types that implement `Display`.
21 ///
22 /// ```ignore
23 /// let result: impl Display = ...;
24 /// verify_that!(result, displays_as(eq(format!("{}", result))))?;
25 /// ```
displays_as<T: Debug + Display, InnerMatcher: Matcher<ActualT = String>>( inner: InnerMatcher, ) -> impl Matcher<ActualT = T>26 pub fn displays_as<T: Debug + Display, InnerMatcher: Matcher<ActualT = String>>(
27 inner: InnerMatcher,
28 ) -> impl Matcher<ActualT = T> {
29 DisplayMatcher::<T, _> { inner, phantom: Default::default() }
30 }
31
32 struct DisplayMatcher<T, InnerMatcher: Matcher> {
33 inner: InnerMatcher,
34 phantom: PhantomData<T>,
35 }
36
37 impl<T: Debug + Display, InnerMatcher: Matcher<ActualT = String>> Matcher
38 for DisplayMatcher<T, InnerMatcher>
39 {
40 type ActualT = T;
41
matches(&self, actual: &T) -> MatcherResult42 fn matches(&self, actual: &T) -> MatcherResult {
43 self.inner.matches(&format!("{actual}"))
44 }
45
explain_match(&self, actual: &T) -> Description46 fn explain_match(&self, actual: &T) -> Description {
47 format!("which displays as a string {}", self.inner.explain_match(&format!("{actual}")))
48 .into()
49 }
50
describe(&self, matcher_result: MatcherResult) -> Description51 fn describe(&self, matcher_result: MatcherResult) -> Description {
52 match matcher_result {
53 MatcherResult::Match => {
54 format!("displays as a string which {}", self.inner.describe(MatcherResult::Match))
55 .into()
56 }
57 MatcherResult::NoMatch => format!(
58 "doesn't display as a string which {}",
59 self.inner.describe(MatcherResult::Match)
60 )
61 .into(),
62 }
63 }
64 }
65
66 #[cfg(test)]
67 mod tests {
68 use super::displays_as;
69 use crate::prelude::*;
70 use indoc::indoc;
71 use std::fmt::{Debug, Display, Error, Formatter};
72
73 #[test]
display_matches_i32() -> Result<()>74 fn display_matches_i32() -> Result<()> {
75 let value = 32;
76 verify_that!(value, displays_as(eq("32")))?;
77 Ok(())
78 }
79
80 #[test]
display_matches_str() -> Result<()>81 fn display_matches_str() -> Result<()> {
82 let value = "32";
83 verify_that!(value, displays_as(eq("32")))?;
84 Ok(())
85 }
86
87 #[test]
display_matches_struct() -> Result<()>88 fn display_matches_struct() -> Result<()> {
89 #[allow(dead_code)]
90 #[derive(Debug)]
91 struct Struct {
92 a: i32,
93 b: i64,
94 }
95 impl Display for Struct {
96 fn fmt(&self, f: &mut Formatter<'_>) -> std::result::Result<(), Error> {
97 write!(f, "{:?}", self)
98 }
99 }
100 verify_that!(Struct { a: 123, b: 321 }, displays_as(eq("Struct { a: 123, b: 321 }")))?;
101 Ok(())
102 }
103
104 #[test]
display_displays_error_message_with_explanation_from_inner_matcher() -> Result<()>105 fn display_displays_error_message_with_explanation_from_inner_matcher() -> Result<()> {
106 let result = verify_that!("123\n234", displays_as(eq("123\n345")));
107
108 verify_that!(
109 result,
110 err(displays_as(contains_substring(indoc!(
111 "
112 Actual: \"123\\n234\",
113 which displays as a string which isn't equal to \"123\\n345\"
114 Difference(-actual / +expected):
115 123
116 -234
117 +345
118 "
119 ))))
120 )
121 }
122 }
123