refactor: DirtyReason::FreshBuild to represent build from scratch

the only beahvior change in this commit is that source verification is
also performed for `DirtyReason::Forced`.

Author: weihanglo

src/cargo/core/compiler/fingerprint/dirty_reason.rs

@@ -77,6 +77,8 @@ pub enum DirtyReason {
     FsStatusOutdated(FsStatus),
     NothingObvious,
     Forced,
+    /// First time to build something.
+    FreshBuild,
 }
 
 trait ShellExt {
@@ -131,6 +133,11 @@ impl fmt::Display for After {
 }
 
 impl DirtyReason {
+    /// Whether a build is dirty because it is a fresh build being kicked off.
+    pub fn is_fresh_build(&self) -> bool {
+        matches!(self, DirtyReason::FreshBuild)
+    }
+
     fn after(old_time: FileTime, new_time: FileTime, what: &'static str) -> After {
         After {
             old_time,
@@ -257,6 +264,7 @@ impl DirtyReason {
                 s.dirty_because(unit, "the fingerprint comparison turned up nothing obvious")
             }
             DirtyReason::Forced => s.dirty_because(unit, "forced"),
+            DirtyReason::FreshBuild => s.dirty_because(unit, "fresh build"),
         }
     }
 }

src/cargo/core/compiler/fingerprint/mod.rs

@@ -415,42 +415,27 @@ pub fn prepare_target(cx: &mut Context<'_, '_>, unit: &Unit, force: bool) -> Car
     // information about failed comparisons to aid in debugging.
     let fingerprint = calculate(cx, unit)?;
     let mtime_on_use = cx.bcx.config.cli_unstable().mtime_on_use;
-    let compare = compare_old_fingerprint(unit, &loc, &*fingerprint, mtime_on_use);
+    let dirty_reason = compare_old_fingerprint(unit, &loc, &*fingerprint, mtime_on_use, force);
 
-    // If our comparison failed or reported dirty (e.g., we're going to trigger
-    // a rebuild of this crate), then we also ensure the source of the crate
-    // passes all verification checks before we build it.
+    let Some(dirty_reason) = dirty_reason else {
+        return Ok(Job::new_fresh());
+    };
+
+    // We're going to rebuild, so ensure the source of the crate passes all
+    // verification checks before we build it.
     //
     // The `Source::verify` method is intended to allow sources to execute
     // pre-build checks to ensure that the relevant source code is all
     // up-to-date and as expected. This is currently used primarily for
     // directory sources which will use this hook to perform an integrity check
     // on all files in the source to ensure they haven't changed. If they have
     // changed then an error is issued.
-    if compare
-        .as_ref()
-        .map(|dirty| dirty.is_some())
-        .unwrap_or(true)
-    {
-        let source_id = unit.pkg.package_id().source_id();
-        let sources = bcx.packages.sources();
-        let source = sources
-            .get(source_id)
-            .ok_or_else(|| internal("missing package source"))?;
-        source.verify(unit.pkg.package_id())?;
-    }
-
-    let dirty_reason = match compare {
-        Ok(None) => {
-            if force {
-                Some(DirtyReason::Forced)
-            } else {
-                return Ok(Job::new_fresh());
-            }
-        }
-        Ok(reason) => reason,
-        Err(_) => None,
-    };
+    let source_id = unit.pkg.package_id().source_id();
+    let sources = bcx.packages.sources();
+    let source = sources
+        .get(source_id)
+        .ok_or_else(|| internal("missing package source"))?;
+    source.verify(unit.pkg.package_id())?;
 
     // Clear out the old fingerprint file if it exists. This protects when
     // compilation is interrupted leaving a corrupt file. For example, a
@@ -521,7 +506,7 @@ pub fn prepare_target(cx: &mut Context<'_, '_>, unit: &Unit, force: bool) -> Car
         Work::new(move |_| write_fingerprint(&loc, &fingerprint))
     };
 
-    Ok(Job::new_dirty(write_fingerprint, dirty_reason))
+    Ok(Job::new_dirty(write_fingerprint, Some(dirty_reason)))
 }
 
 /// Dependency edge information for fingerprints. This is generated for each
@@ -1755,10 +1740,15 @@ fn compare_old_fingerprint(
     old_hash_path: &Path,
     new_fingerprint: &Fingerprint,
     mtime_on_use: bool,
-) -> CargoResult<Option<DirtyReason>> {
+    forced: bool,
+) -> Option<DirtyReason> {
     let compare = _compare_old_fingerprint(old_hash_path, new_fingerprint, mtime_on_use);
     log_compare(unit, &compare);
-    compare
+    match compare {
+        Ok(None) if forced => Some(DirtyReason::Forced),
+        Ok(reason) => reason,
+        Err(_) => Some(DirtyReason::FreshBuild),
+    }
 }
 
 fn _compare_old_fingerprint(

src/cargo/core/compiler/job_queue/mod.rs

@@ -1111,9 +1111,11 @@ impl<'cfg> DrainState<'cfg> {
             // being a compiled package.
             Dirty(dirty_reason) => {
                 if let Some(reason) = dirty_reason {
-                    config
-                        .shell()
-                        .verbose(|shell| reason.present_to(shell, unit, ws_root))?;
+                    if !reason.is_fresh_build() {
+                        config
+                            .shell()
+                            .verbose(|shell| reason.present_to(shell, unit, ws_root))?;
+                    }
                 }
 
                 if unit.mode.is_doc() {