Add require_full_match option (#448)

May need some refining. Closes #351, but with an additional option, since `force_update` seems like a bad term for this

cargo-insta/src/cli.rs

@@ -891,6 +891,9 @@ fn prepare_test_runner<'snapshot_ref>(
     if cmd.require_full_match {
         proc.env("INSTA_REQUIRE_FULL_MATCH", "1");
     }
+    if cmd.require_full_match {
+        proc.env("INSTA_REQUIRE_FULL_MATCH", "1");
+    }
     let glob_filter =
         cmd.glob_filter
             .iter()

src/env.rs

@@ -98,6 +98,7 @@ impl std::error::Error for Error {
 pub struct ToolConfig {
     force_update_snapshots: bool,
     force_pass: bool,
+    require_full_match: bool,
     output: OutputBehavior,
     snapshot_update: SnapshotUpdate,
     #[cfg(feature = "glob")]
@@ -157,6 +158,14 @@ impl ToolConfig {
                 Ok("1") => true,
                 _ => return Err(Error::Env("INSTA_FORCE_UPDATE")),
             },
+            require_full_match: match env::var("INSTA_REQUIRE_FULL_MATCH").as_deref() {
+                Err(_) | Ok("") => resolve(&cfg, &["behavior", "require_full_match"])
+                    .and_then(|x| x.as_bool())
+                    .unwrap_or(false),
+                Ok("0") => false,
+                Ok("1") => true,
+                _ => return Err(Error::Env("INSTA_REQUIRE_FULL_MATCH")),
+            },
             force_pass: match env::var("INSTA_FORCE_PASS").as_deref() {
                 Err(_) | Ok("") => resolve(&cfg, &["behavior", "force_pass"])
                     .and_then(|x| x.as_bool())
@@ -255,6 +264,11 @@ impl ToolConfig {
         self.force_update_snapshots
     }
 
+    /// Should we fail if metadata doesn't match?
+    pub fn require_full_match(&self) -> bool {
+        self.require_full_match
+    }
+
     /// Is insta instructed to fail in tests?
     pub fn force_pass(&self) -> bool {
         self.force_pass

src/lib.rs

@@ -196,6 +196,8 @@
 //! behavior:
 //!   # also set by INSTA_FORCE_UPDATE
 //!   force_update: true/false
+//!   # also set by INSTA_REQUIRE_FULL_MATCH
+//!   require_full_match: true/false
 //!   # also set by INSTA_FORCE_PASS
 //!   force_pass: true/false
 //!   # also set by INSTA_OUTPUT

src/runtime.rs

@@ -666,8 +666,19 @@ pub fn assert_snapshot(
         }
     });
 
-    // pass if the snapshots are missing
-    if ctx.old_snapshot.as_ref().map(|x| x.contents()) == Some(new_snapshot.contents()) {
+    let pass = ctx
+        .old_snapshot
+        .as_ref()
+        .map(|x| {
+            if tool_config.require_full_match() {
+                x.matches_fully(&new_snapshot)
+            } else {
+                x.matches(&new_snapshot)
+            }
+        })
+        .unwrap_or(false);
+
+    if pass {
         ctx.cleanup_passing()?;
 
         if tool_config.force_update_snapshots() {

src/snapshot.rs

@@ -128,7 +128,7 @@ impl PendingInlineSnapshot {
 }
 
 /// Snapshot metadata information.
-#[derive(Debug, Default, Clone)]
+#[derive(Debug, Default, Clone, PartialEq)]
 pub struct MetaData {
     /// The source file (relative to workspace root).
     pub(crate) source: Option<String>,
@@ -434,6 +434,16 @@ impl Snapshot {
         &self.snapshot
     }
 
+    /// Snapshot contents match another snapshot's.
+    pub fn matches(&self, other: &Snapshot) -> bool {
+        self.contents() == other.contents()
+    }
+
+    /// Snapshot contents _and_ metadata match another snapshot's.
+    pub fn matches_fully(&self, other: &Snapshot) -> bool {
+        self.matches(other) && self.metadata == other.metadata
+    }
+
     /// The snapshot contents as a &str
     pub fn contents_str(&self) -> &str {
         self.snapshot.as_str()