Fix --require-full-match on inline snapshots with leading newlines

cargo-insta/tests/main.rs

@@ -1024,20 +1024,27 @@ fn test_linebreaks() {
 
     assert!(&output.status.success());
 
-    assert_snapshot!(test_project.diff("src/lib.rs"), @r#####"
-    --- Original: src/lib.rs
-    +++ Updated: src/lib.rs
-    @@ -1,8 +1,5 @@
-
-     #[test]
-     fn test_linebreaks() {
-    -    insta::assert_snapshot!("foo", @r####"
-    -    foo
-    -    
-    -    "####);
-    +    insta::assert_snapshot!("foo", @"foo");
-     }
-    "#####);
+    // When #563 merges, or #630 is resolved, this will change the snapshot. I
+    // also think it's possible to have it work sooner, but have iterated quite
+    // a few times trying to get this to work, and then finding something else
+    // without test coverage didn't work; so not sure it's a great investment of
+    // time.
+    assert_snapshot!(test_project.diff("src/lib.rs"), @"");
+
+    // assert_snapshot!(test_project.diff("src/lib.rs"), @r#####"
+    // --- Original: src/lib.rs
+    // +++ Updated: src/lib.rs
+    // @@ -1,8 +1,5 @@
+
+    //  #[test]
+    //  fn test_linebreaks() {
+    // -    insta::assert_snapshot!("foo", @r####"
+    // -    foo
+    // -
+    // -    "####);
+    // +    insta::assert_snapshot!("foo", @"foo");
+    //  }
+    // "#####);
 }
 
 #[test]
@@ -1123,48 +1130,83 @@ fn test_wrong_indent_force() {
         )
         .create_project();
 
-    // Confirm the test passes despite the indent
+    // ...and that it passes with `--require-full-match`. Note that ideally this
+    // would fail, but we can't read the desired indent without serde, which is
+    // in `cargo-insta` only. So this tests the current state rather than the
+    // ideal state (and I don't think there's a reasonable way to get the ideal state)
+    // Now confirm that `--require-full-match` passes
     let output = test_project
         .insta_cmd()
-        .args(["test", "--check", "--", "--nocapture"])
+        .args([
+            "test",
+            "--check",
+            "--require-full-match",
+            "--",
+            "--nocapture",
+        ])
         .output()
         .unwrap();
     assert!(&output.status.success());
+}
+
+#[test]
+fn test_matches_fully_linebreaks() {
+    // Until #563 merges, we should be OK with different leading newlines, even
+    // in exact / full match mode.
+    let test_project = TestFiles::new()
+        .add_file(
+            "Cargo.toml",
+            r#"
+[package]
+name = "exact-match-inline"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+doctest = false
+
+[dependencies]
+insta = { path = '$PROJECT_PATH' }
+"#
+            .to_string(),
+        )
+        .add_file(
+            "src/lib.rs",
+            r#####"
+#[test]
+fn test_additional_linebreak() {
+    // Additional newline here
+    insta::assert_snapshot!(r#"
+
+    (
+        "name_foo",
+        "insta_tests__tests",
+    )
+    "#, @r#"
+    (
+        "name_foo",
+        "insta_tests__tests",
+    )
+    "#);
+}
+"#####
+                .to_string(),
+        )
+        .create_project();
 
-    // Then run the test with --force-update-snapshots and --accept to confirm
-    // the new snapshot is written
+    // Confirm the test passes despite the indent
     let output = test_project
         .insta_cmd()
         .args([
             "test",
-            "--force-update-snapshots",
-            "--accept",
+            "--check",
+            "--require-full-match",
             "--",
             "--nocapture",
         ])
         .output()
         .unwrap();
     assert!(&output.status.success());
-
-    // https://github.com/mitsuhiko/insta/pull/563 will fix the starting &
-    // ending newlines
-    assert_snapshot!(test_project.diff("src/lib.rs"), @r##"
-    --- Original: src/lib.rs
-    +++ Updated: src/lib.rs
-    @@ -4,8 +4,8 @@
-         insta::assert_snapshot!(r#"
-         foo
-         foo
-    -    "#, @r#"
-    -                foo
-    -                foo
-    -    "#);
-    +    "#, @r"
-    +    foo
-    +    foo
-    +    ");
-     }
-    "##);
 }
 
 #[test]

insta/src/snapshot.rs

@@ -528,7 +528,20 @@ impl Snapshot {
     pub fn matches_fully(&self, other: &Self) -> bool {
         match (self.contents(), other.contents()) {
             (SnapshotContents::Text(self_contents), SnapshotContents::Text(other_contents)) => {
-                let contents_match_exact = self_contents == other_contents;
+                // Note that we previously would match the exact values of the
+                // unnormalized text. But that's too strict — it means we can
+                // never match a snapshot that has leading/trailing whitespace.
+                // So instead we check it matches on the latest format.
+                // Generally those should be the same — latest should be doing
+                // the minimum normalization; if they diverge we could update
+                // this to be stricter.
+                //
+                // (I think to do this perfectly, we'd want to match the
+                // _reference_ value unnormalized, but the _generated_ value
+                // normalized. That way, we can get the But at the moment we
+                // don't distinguish between which is which in our data
+                // structures.)
+                let contents_match_exact = self_contents.matches_latest(other_contents);
                 match self_contents.kind {
                     TextSnapshotKind::File => {
                         self.metadata.trim_for_persistence()
@@ -822,8 +835,7 @@ fn min_indentation(snapshot: &str) -> usize {
         .unwrap_or(0)
 }
 
-// Removes excess indentation, removes excess whitespace at start & end
-// and changes newlines to \n.
+/// Removes excess indentation, and changes newlines to \n.
 fn normalize_inline_snapshot(snapshot: &str) -> String {
     let indentation = min_indentation(snapshot);
     snapshot