VSI: Special case filtering

Changelog.md

@@ -2,6 +2,7 @@
 
 ## v2.19.6
 
+- Special cases scans with a single VSI only filter to skip other analysis strategies ([#407](https://github.com/fossas/spectrometer/pull/407))
 - Adds the ability to skip resolving dependencies from FOSSA projects discovered during VSI scans ([#435](https://github.com/fossas/spectrometer/pull/435))
 
 ## v2.19.5
@@ -45,7 +46,7 @@ Use [`fossa-deps.{yml,json}`](docs/features/vendored-dependencies.md) file to fa
 
 ## v2.18.0
 
-- When applicable, fossa-cli uses the cgroup CPU quota (under cfs) to determine the number of runtime threads to use. This dramatically improves runtime speed when we're running within a cpu-limited container on a large machine with many physical processors.
+- Improves performance in scenarios where cgroups are used to limit the amount of CPU time available, such as K8S containers ([#403](https://github.com/fossas/spectrometer/pull/403))
 
 ## v2.17.3
 

src/App/Fossa/Analyze.hs

@@ -71,7 +71,7 @@ import Data.Maybe (catMaybes, fromMaybe)
 import Data.String.Conversion (decodeUtf8)
 import Data.Text (Text)
 import Discovery.Archive qualified as Archive
-import Discovery.Filters (AllFilters, applyFilters)
+import Discovery.Filters (AllFilters, applyFilters, filterIsVSIOnly)
 import Discovery.Projects (withDiscoveredProjects)
 import Effect.Exec (Exec, runExecIO)
 import Effect.Logger (
@@ -254,7 +254,12 @@ runAnalyzers ::
   Path Abs Dir ->
   AllFilters ->
   m ()
-runAnalyzers basedir filters = traverse_ single discoverFuncs
+runAnalyzers basedir filters = do
+  if filterIsVSIOnly filters
+    then do
+      logInfo "Running in VSI only mode, skipping other analyzers"
+      pure ()
+    else traverse_ single discoverFuncs
   where
     single (DiscoverFunc f) = withDiscoveredProjects f basedir (runDependencyAnalysis basedir filters)
 
@@ -341,9 +346,14 @@ analyze (BaseDir basedir) destination override unpackArchives jsonOutput include
 
   -- additional source units are built outside the standard strategy flow, because they either
   -- require additional information (eg API credentials), or they return additional information (eg user deps).
-  manualSrcUnits <- Diag.context "fossa-deps" $ analyzeFossaDepsFile basedir apiOpts
   vsiResults <- Diag.context "analyze-vsi" $ analyzeVSI modeVSIAnalysis apiOpts basedir filters modeVSISkipResolution
   binarySearchResults <- Diag.context "discover-binaries" $ analyzeDiscoverBinaries modeBinaryDiscovery basedir filters
+  manualSrcUnits <-
+    if filterIsVSIOnly filters
+      then do
+        logInfo "Running in VSI only mode, skipping manual source units"
+        pure Nothing
+      else Diag.context "fossa-deps" $ analyzeFossaDepsFile basedir apiOpts
   let additionalSourceUnits :: [SourceUnit]
       additionalSourceUnits = catMaybes [manualSrcUnits, vsiResults, binarySearchResults]
 
@@ -397,8 +407,13 @@ analyzeVSI _ _ _ _ _ = pure Nothing
 
 analyzeDiscoverBinaries :: (MonadIO m, Has Diag.Diagnostics sig m, Has (Lift IO) sig m, Has Logger sig m, Has ReadFS sig m) => BinaryDiscoveryMode -> Path Abs Dir -> AllFilters -> m (Maybe SourceUnit)
 analyzeDiscoverBinaries BinaryDiscoveryEnabled dir filters = do
-  logInfo "Discovering binary files as dependencies"
-  analyzeBinaryDeps dir filters
+  if filterIsVSIOnly filters
+    then do
+      logInfo "Running in VSI only mode, skipping binary discovery"
+      pure Nothing
+    else do
+      logInfo "Discovering binary files as dependencies"
+      analyzeBinaryDeps dir filters
 analyzeDiscoverBinaries _ _ _ = pure Nothing
 
 doAssertRevisionBinaries :: (Has Diag.Diagnostics sig m, Has ReadFS sig m, Has (Lift IO) sig m, Has Logger sig m) => IATAssertionMode -> ApiOpts -> Locator -> m ()

src/Discovery/Filters.hs

@@ -1,3 +1,5 @@
+{-# LANGUAGE RecordWildCards #-}
+
 module Discovery.Filters (
   AllFilters (..),
   targetFilterParser,
@@ -6,6 +8,7 @@ module Discovery.Filters (
   FilterMatch (..),
   FilterResult (..),
   apply,
+  filterIsVSIOnly,
 ) where
 
 import Data.List ((\\))
@@ -28,6 +31,18 @@ import Text.Megaparsec (
 import Text.Megaparsec.Char (alphaNumChar, char)
 import Types (BuildTarget (..), FoundTargets (FoundTargets, ProjectWithoutTargets), TargetFilter (..))
 
+-- | filterIsVSIOnly is a very naive check for whether the user provided a filter for the VSI target *only*, at the root of the project with no path specified.
+-- This decision was made because predicating VSI only scans is a stopgap until we have more broad support for *preemptive* analysis filtering.
+-- VSI supports very large scans that the rest of our analysis may not.
+filterIsVSIOnly :: AllFilters -> Bool
+filterIsVSIOnly AllFilters{..} = do
+  let includes = combinedTargets includeFilters
+  length includes == 1 && any matches includes
+  where
+    matches f = case f of
+      TypeTarget name -> name == "vsi"
+      _ -> False
+
 data AllFilters = AllFilters
   { legacyFilters :: [TargetFilter]
   , includeFilters :: FilterCombination