Fix logic for dumping MLIR modules (#1070)

In certain cases we were _always_ dumping the modules even with a successful
compilation and `DUMP_MLIR_ALWAYS=false`.  Add also a relevant test to catch
this mistake.

Author: giordano

src/mlir/IR/Pass.jl

@@ -107,7 +107,9 @@ function try_compile_dump_mlir(f, mod::Module, pm=nothing)
         failed = true
         rethrow()
     finally
-        dump_mlir(mod, pm; failed)
+        if failed || DUMP_MLIR_ALWAYS[]
+            dump_mlir(mod, pm; failed)
+        end
     end
 end
 

test/basic.jl

@@ -1087,16 +1087,24 @@ end
     always_old = Reactant.MLIR.IR.DUMP_MLIR_ALWAYS[]
     dir_old = Reactant.MLIR.IR.DUMP_MLIR_DIR[]
 
-    Reactant.MLIR.IR.DUMP_MLIR_ALWAYS[] = true
-
     mktempdir() do dir
+        Reactant.MLIR.IR.DUMP_MLIR_ALWAYS[] = true
         Reactant.MLIR.IR.DUMP_MLIR_DIR[] = dir
         @compile sin.(Reactant.to_rarray(Float32[1.0]))
         for mod in readdir(dir; join=true)
             @test contains(read(mod, String), "hlo.sine")
         end
     end
 
+    mktempdir() do dir
+        Reactant.MLIR.IR.DUMP_MLIR_ALWAYS[] = false
+        Reactant.MLIR.IR.DUMP_MLIR_DIR[] = dir
+        @compile exp.(Reactant.to_rarray(Float32[1.0]))
+        # Make sure we don't save anything to file when compilation is
+        # successful and `DUMP_MLIR_ALWAYS=false`.
+        @test isempty(readdir(dir; join=true))
+    end
+
     Reactant.MLIR.IR.DUMP_MLIR_ALWAYS[] = always_old
     Reactant.MLIR.IR.DUMP_MLIR_DIR[] = dir_old
 end