Remove --upgrade from pip install in the pip and functions-framework …

…buildpack

Some dependencies are incompatible with the --upgrade and --target flag combination, e.g. pypa/pip#8799.

PiperOrigin-RevId: 328384678
Change-Id: Iea6962774a6bd82f02435ba785ba92445e762c8d

cmd/python/pip/main.go

@@ -62,10 +62,14 @@ func buildFn(ctx *gcp.Context) error {
 		return nil
 	}
 	ctx.CacheMiss(layerName)
+	// pip install --target does no override existing dependencies, so remove everything.
+	// We cannot use --upgrade due to a bug in pip: https://github.com/pypa/pip/issues/8799.
+	// Any cached dependencies will be restored from PIP_CACHE_DIR.
+	ctx.ClearLayer(l)
 
 	// Install modules in requirements.txt.
 	ctx.Logf("Running pip install.")
-	ctx.Exec([]string{"python3", "-m", "pip", "install", "--upgrade", "-r", "requirements.txt", "-t", l.Path}, gcp.WithEnv("PIP_CACHE_DIR="+cl.Path), gcp.WithUserAttribution)
+	ctx.Exec([]string{"python3", "-m", "pip", "install", "-r", "requirements.txt", "--target", l.Path}, gcp.WithEnv("PIP_CACHE_DIR="+cl.Path), gcp.WithUserAttribution)
 
 	l.SharedEnvironment.PrependPath("PYTHONPATH", l.Path)
 

pkg/python/python.go

@@ -103,7 +103,10 @@ func InstallRequirements(ctx *gcp.Context, l *libcnb.Layer, req string) error {
 		ctx.CacheHit(l.Name)
 	} else {
 		ctx.CacheMiss(l.Name)
-		ctx.Exec([]string{"python3", "-m", "pip", "install", "-t", l.Path, "-r", req}, gcp.WithUserAttribution)
+		// pip install --target does no override existing dependencies, so remove everything.
+		// We cannot use --upgrade due to a bug in pip: https://github.com/pypa/pip/issues/8799.
+		ctx.ClearLayer(l)
+		ctx.Exec([]string{"python3", "-m", "pip", "install", "-r", req, "--target", l.Path}, gcp.WithUserAttribution)
 	}
 	l.SharedEnvironment.PrependPath("PYTHONPATH", l.Path)
 	return nil