fix: force cache bust when --no-cache used (#4157)

fixes #2593

Signed-off-by: Alex Couture-Beil <[email protected]>

earthfile2llb/converter.go

@@ -51,6 +51,7 @@ import (
 	"github.com/earthly/earthly/util/vertexmeta"
 	"github.com/earthly/earthly/variables"
 	"github.com/earthly/earthly/variables/reserved"
+	"github.com/google/uuid"
 	"github.com/moby/buildkit/client/llb"
 	dockerimage "github.com/moby/buildkit/exporter/containerimage/image"
 	"github.com/moby/buildkit/frontend/dockerfile/dockerfile2llb"
@@ -2306,6 +2307,10 @@ func (c *Converter) internalRun(ctx context.Context, opts ConvertRunOpts) (pllb.
 	// Shell and debugger wrap.
 	prependDebugger := !opts.Locally
 	finalArgs = opts.shellWrap(finalArgs, extraEnvVars, opts.WithShell, prependDebugger, isInteractive)
+	if opts.NoCache {
+		// llb.IgnoreCache is not always enough; we will force a different cache key as a work-around
+		finalArgs = append(finalArgs, "#"+uuid.NewString())
+	}
 	if opts.Locally {
 		// buildkit-hack in order to run locally, we prepend the command with a magic UUID.
 		finalArgs = append(

tests/Earthfile

@@ -216,7 +216,7 @@ ga-no-qemu-group12:
     BUILD --pass-args ./warn-if-not-logged-in+test
     BUILD --pass-args ./with-docker-validate-labels+all
     BUILD --pass-args +test-aws-oidc
-
+    BUILD --pass-args +run-no-cache-save-artifact
 
 ga-no-qemu-slow:
     BUILD +server
@@ -1061,6 +1061,26 @@ run-no-cache:
     DO +RUN_EARTHLY --earthfile=run-no-cache.earth --use_tmpfs=false --target=+test-from \
         --grep_flags="-v" --output_contains="\\\*cached\\\* --> .*motd2 \\\.\\\//"
 
+run-no-cache-save-artifact:
+    # based on https://github.com/earthly/earthly/issues/2593#issuecomment-1777657111
+    COPY run-no-cache-save-artifact.earth Earthfile
+    RUN touch some-file
+    LET numruns=10
+    RUN echo "#!/bin/sh
+set -ex
+for x in \$(seq 1 $numruns); do
+  earthly --config \$earthly_config --artifact '+build/*' test/\$x/
+done
+" >/tmp/test-earthly-script && chmod +x /tmp/test-earthly-script
+    ENV EARTHLY_EXEC_CMD="/tmp/test-earthly-script"
+    RUN --privileged \
+    --entrypoint \
+    --mount=type=tmpfs,target=/tmp/earthly \
+    -- -P
+    # test that all output files are different
+    RUN cat test/*/dep1
+    RUN acbtest "$(cat test/*/dep1 | sort | uniq | wc -l)" = "$numruns"
+
 save-artifact-after-push:
     # test that save after push only outputs files before the RUN --push
     DO +RUN_EARTHLY --earthfile=save-artifact-after-push.earth --target=+test

tests/run-no-cache-save-artifact.earth

@@ -0,0 +1,20 @@
+VERSION 0.8
+
+FROM alpine:3.18
+WORKDIR /work-der-work
+
+build:
+    COPY +dep2/out dep2
+    COPY +dep1/out dep1
+    RUN rm dep2
+    SAVE ARTIFACT dep1
+
+dep1:
+    COPY some-file . # required to trigger bug
+    COPY +dep2/out dep2
+    RUN cp dep2 out
+    SAVE ARTIFACT out
+
+dep2:
+    RUN --no-cache head -c 20 /dev/urandom | base64 > out
+    SAVE ARTIFACT out