Bad arg-type error shown (but ignored) for Files/write invocation

[rbrw]

Perhaps the code below is incorrect somehow, but if not, I see an error like this

Error: Bad arg-type nil for method named write for class java.nio.file.Files, full arg type li
st (java.lang.Object, [B, nil).  ast pprinted below for debugging tools.analyzer:
{:op :static-call,
 :children [:args],
 :eastwood/path [3 :init :expr :methods 0 :body :ret :statements 0],
 :tag java.nio.file.Path,
 :form
 ^{:line 17}

when running eastwood on this code:

(ns eastwood-error.core
  (:gen-class)
  (:import
   (java.nio.file Files OpenOption)))

(defmacro ignore-value
  "Suppress eastwood's unused-ret-vals warning:
  https://github.com/jonase/eastwood#unused-ret-vals.  See
  ./eastwood.clj for the suppression that makes this work."
  [x]
  `(do ~x nil))

(defn crash? [path item]
  (ignore-value
   (Files/write path (byte-array 10) (into-array OpenOption []))))

and it's presence doesn't seem to matter, bu the ./eastwood.clj suppression was:

(disable-warning
 {:linter :unused-ret-vals
  :if-inside-macroexpansion-of #{'some.where/ignore-value}
  :within-depth 2
  :reason "ignore-value is intended to suppress this linter."})

[rbrw]

Oh, and changing the body of ignore-value to do this instead avoids the error report:

`(let [x# ~x]
   nil)

[vemv]

Hi!

Could you post the original code (i.e. without a workaround) and if needed, an explanation of what it does / the problem faced?

[rbrw]

That code was intended to demonstrate the problem, i.e. if you run eastwood on that file it produces an extensive bad arg-type error that I didn't expect, though that doesn't actually seem to cause eastwood to fail in the end (exit status is still 0). And as mentioned, changing the definition of the ignore-value macro from the do to the let avoids the errror.

However, now I see that the real source of the issue (if there is one) is the Files/write call itself. Running eastwood 0.3.14 (Clojure 1.10.2) on this file:

(ns eastwood-error.core
  (:gen-class)
  (:import
   (java.nio.file Files OpenOption Path)))

(defn do-something [path x]
  ;; ...
  (Files/write path (byte-array 10) (into-array OpenOption []))
  ;; ...
  true)

produces the crash, and adding a single ^Path type annotation avoids it:

(defn do-something [^Path path x]
  ;; ...
  (Files/write path (byte-array 10) (into-array OpenOption []))
  ;; ...
  true)

So I wondered if that (ignored) error was expected or a bug.

Also, adding the ^Path annotation reveals an unused-ret-vals complaint:

src/eastwood_error/core.clj:8:3: unused-ret-vals: Should use return value of static method call, but it is discarded: (. java.nio.file.Files (write path (byte-array 10) (into-array OpenOption [])))

I created the ignore-values macro to suppress those, but is that a reasonable approach, or is there some preferred way?

Thanks

[vemv]

Thank you, can reproduce.

Adding the following to the Eastwood repo:

(ns eastwood.foo
  (:import
   (java.nio.file Files OpenOption Path)))

(defn do-something [path x]
  ;; ...
  (Files/write path (byte-array 10) (into-array OpenOption []))
  ;; ...
  true)

...will result in the following output:

Details

~/eastwood (master) $ ~/bin/lein-latest eastwood "{:namespaces [eastwood.foo]}"
== Eastwood 0.3.14 Clojure 1.10.1 JVM 1.8.0_281 ==
Directories scanned for source files:


== Linting eastwood.foo ==
src/eastwood/foo.clj:7:3: Reflection warning - call to static method write on java.nio.file.Files can't be resolved (argument types: unknown, [B, unknown).
Error: Bad arg-type nil for method named write for class java.nio.file.Files, full arg type list (java.lang.Object, [B, nil).  ast pprinted below for debugging tools.analyzer:
{:op :static-call,
 :children [:args],
 :eastwood/path [1 :init :expr :methods 0 :body :statements 0],
 :tag java.nio.file.Path,
 :form
 ^{:line 7}
 (.
  java.nio.file.Files
  (write
   ^{:line 7} path
   ^{:line 7} (^{:line 7} byte-array 10)
   ^{:line 7}
   (^{:line 7} into-array ^{:line 7} OpenOption ^{:line 7} []))),
 :raw-forms
 (^{:line 7,
    :eastwood.copieddeps.dep1.clojure.tools.analyzer/resolved-op nil}
  (^{:line 7} Files/write
   ^{:line 7} path
   ^{:line 7} (^{:line 7} byte-array 10)
   ^{:line 7}
   (^{:line 7} into-array ^{:line 7} OpenOption ^{:line 7} []))),
 :class java.nio.file.Files,
 :args
 [{:op :local,
   :children [],
   :eastwood/path
   [1 :init :expr :methods 0 :body :statements 0 :args 0],
   :tag java.lang.Object,
   :form ^{:line 7} path,
   :local :arg,
   :arg-id 0,
   :assignable? false,
   :atom #<Atom@32050628: {:tag java.lang.Object}>,
   :name path__#0,
   :o-tag java.lang.Object,
   :variadic? false}
  {:op :static-call,
   :children [:args],
   :eastwood/path
   [1 :init :expr :methods 0 :body :statements 0 :args 1],
   :tag [B,
   :form
   ^{:line 7} (. clojure.lang.Numbers clojure.core/byte_array 10),
   :raw-forms
   (^{:line 7,
      :eastwood.copieddeps.dep1.clojure.tools.analyzer/resolved-op
      ^{:added "1.1",
        :ns
        ^{:doc "Fundamental library of the Clojure language",
          :author "Rich Hickey"}
        #object[clojure.lang.Namespace 0x4f629aa4 "clojure.core"],
        :name byte-array,
        :file "clojure/core.clj",
        :inline-arities #{1 2},
        :column 1,
        :line 5293,
        :arglists ([size-or-seq] [size init-val-or-seq]),
        :doc "Creates an array of bytes",
        :inline
        #object[clojure.core$byte_array__inliner__6496 0xf245168 "clojure.core$byte_array__inliner__6496@f245168"]}
      #'clojure.core/byte-array}
    (^{:line 7} byte-array 10)),
   :class clojure.lang.Numbers,
   :args
   [{:op :const,
     :eastwood/path
     [1 :init :expr :methods 0 :body :statements 0 :args 1 :args 0],
     :tag java.lang.Object,
     :form 10,
     :val 10,
     :literal? true,
     :o-tag long,
     :type :number}],
   :method byte_array,
   :o-tag [B,
   :validated? true}
  {:op :invoke,
   :children [:fn :args],
   :eastwood/path
   [1 :init :expr :methods 0 :body :statements 0 :args 2],
   :form
   ^{:line 7}
   (^{:line 7} into-array ^{:line 7} OpenOption ^{:line 7} []),
   :fn
   {:op :var,
    :eastwood/path
    [1 :init :expr :methods 0 :body :statements 0 :args 2 :fn],
    :form ^{:line 7} into-array,
    :var
    ^{:added "1.0",
      :ns
      ^{:doc "Fundamental library of the Clojure language",
        :author "Rich Hickey"}
      #object[clojure.lang.Namespace 0x4f629aa4 "clojure.core"],
      :name into-array,
      :file "clojure/core.clj",
      :static true,
      :column 1,
      :line 3443,
      :arglists ([aseq] [type aseq]),
      :doc
      "Returns an array with components set to the values in aseq. The array's\n  component type is type if provided, or the type of the first value in\n  aseq if present, or Object. All values in aseq must be compatible with\n  the component type. Class objects for the primitive types can be obtained\n  using, e.g., Integer/TYPE."}
    #'clojure.core/into-array,
    :meta
    {:added "1.0",
     :ns
     ^{:doc "Fundamental library of the Clojure language",
       :author "Rich Hickey"}
     #object[clojure.lang.Namespace 0x4f629aa4 "clojure.core"],
     :name into-array,
     :file "clojure/core.clj",
     :static true,
     :column 1,
     :line 3443,
     :arglists ([aseq] [type aseq]),
     :doc
     "Returns an array with components set to the values in aseq. The array's\n  component type is type if provided, or the type of the first value in\n  aseq if present, or Object. All values in aseq must be compatible with\n  the component type. Class objects for the primitive types can be obtained\n  using, e.g., Integer/TYPE."},
    :arglists ([aseq] [type aseq]),
    :assignable? false,
    :o-tag java.lang.Object},
   :args
   [{:op :const,
     :eastwood/path
     [1 :init :expr :methods 0 :body :statements 0 :args 2 :args 0],
     :tag java.lang.Class,
     :form ^{:line 7} OpenOption,
     :val java.nio.file.OpenOption,
     :literal? true,
     :o-tag java.lang.Class,
     :type :class}
    {:op :with-meta,
     :children [:meta :expr],
     :eastwood/path
     [1 :init :expr :methods 0 :body :statements 0 :args 2 :args 1],
     :tag clojure.lang.PersistentVector,
     :form ^{:line 7} [],
     :meta
     {:op :const,
      :eastwood/path
      [1
       :init
       :expr
       :methods
       0
       :body
       :statements
       0
       :args
       2
       :args
       1
       :meta],
      :tag clojure.lang.PersistentArrayMap,
      :form
      {:file "eastwood/foo.clj",
       :line 7,
       :column 60,
       :end-line 7,
       :end-column 62},
      :val
      {:file "eastwood/foo.clj",
       :line 7,
       :column 60,
       :end-line 7,
       :end-column 62},
      :literal? true,
      :o-tag clojure.lang.PersistentArrayMap,
      :type :map},
     :expr
     {:op :vector,
      :children [:items],
      :eastwood/path
      [1
       :init
       :expr
       :methods
       0
       :body
       :statements
       0
       :args
       2
       :args
       1
       :expr],
      :tag clojure.lang.PersistentVector,
      :form ^{:line 7} [],
      :items [],
      :o-tag clojure.lang.PersistentVector},
     :o-tag java.lang.Object}],
   :meta
   {:file "eastwood/foo.clj",
    :line 7,
    :column 37,
    :end-line 7,
    :end-column 63},
   :o-tag java.lang.Object}],
 :method write,
 :o-tag java.lang.Object}
Error: Bad arg-type nil for method named write for class java.nio.file.Files, full arg type list (java.lang.Object, [B, nil).  ast pprinted below for debugging tools.analyzer:
{:op :static-call,
 :children [:args],
 :eastwood/path [1 :init :expr :methods 0 :body :statements 0],
 :tag java.nio.file.Path,
 :form
 ^{:line 7}
 (.
  java.nio.file.Files
  (write
   ^{:line 7} path
   ^{:line 7} (^{:line 7} byte-array 10)
   ^{:line 7}
   (^{:line 7} into-array ^{:line 7} OpenOption ^{:line 7} []))),
 :raw-forms
 (^{:line 7,
    :eastwood.copieddeps.dep1.clojure.tools.analyzer/resolved-op nil}
  (^{:line 7} Files/write
   ^{:line 7} path
   ^{:line 7} (^{:line 7} byte-array 10)
   ^{:line 7}
   (^{:line 7} into-array ^{:line 7} OpenOption ^{:line 7} []))),
 :class java.nio.file.Files,
 :args
 [{:op :local,
   :children [],
   :eastwood/path
   [1 :init :expr :methods 0 :body :statements 0 :args 0],
   :tag java.lang.Object,
   :form ^{:line 7} path,
   :local :arg,
   :arg-id 0,
   :assignable? false,
   :atom #<Atom@32050628: {:tag java.lang.Object}>,
   :name path__#0,
   :o-tag java.lang.Object,
   :variadic? false}
  {:op :static-call,
   :children [:args],
   :eastwood/path
   [1 :init :expr :methods 0 :body :statements 0 :args 1],
   :tag [B,
   :form
   ^{:line 7} (. clojure.lang.Numbers clojure.core/byte_array 10),
   :raw-forms
   (^{:line 7,
      :eastwood.copieddeps.dep1.clojure.tools.analyzer/resolved-op
      ^{:added "1.1",
        :ns
        ^{:doc "Fundamental library of the Clojure language",
          :author "Rich Hickey"}
        #object[clojure.lang.Namespace 0x4f629aa4 "clojure.core"],
        :name byte-array,
        :file "clojure/core.clj",
        :inline-arities #{1 2},
        :column 1,
        :line 5293,
        :arglists ([size-or-seq] [size init-val-or-seq]),
        :doc "Creates an array of bytes",
        :inline
        #object[clojure.core$byte_array__inliner__6496 0xf245168 "clojure.core$byte_array__inliner__6496@f245168"]}
      #'clojure.core/byte-array}
    (^{:line 7} byte-array 10)),
   :class clojure.lang.Numbers,
   :args
   [{:op :const,
     :eastwood/path
     [1 :init :expr :methods 0 :body :statements 0 :args 1 :args 0],
     :tag java.lang.Object,
     :form 10,
     :val 10,
     :literal? true,
     :o-tag long,
     :type :number}],
   :method byte_array,
   :o-tag [B,
   :validated? true}
  {:op :invoke,
   :children [:fn :args],
   :eastwood/path
   [1 :init :expr :methods 0 :body :statements 0 :args 2],
   :form
   ^{:line 7}
   (^{:line 7} into-array ^{:line 7} OpenOption ^{:line 7} []),
   :fn
   {:op :var,
    :eastwood/path
    [1 :init :expr :methods 0 :body :statements 0 :args 2 :fn],
    :form ^{:line 7} into-array,
    :var
    ^{:added "1.0",
      :ns
      ^{:doc "Fundamental library of the Clojure language",
        :author "Rich Hickey"}
      #object[clojure.lang.Namespace 0x4f629aa4 "clojure.core"],
      :name into-array,
      :file "clojure/core.clj",
      :static true,
      :column 1,
      :line 3443,
      :arglists ([aseq] [type aseq]),
      :doc
      "Returns an array with components set to the values in aseq. The array's\n  component type is type if provided, or the type of the first value in\n  aseq if present, or Object. All values in aseq must be compatible with\n  the component type. Class objects for the primitive types can be obtained\n  using, e.g., Integer/TYPE."}
    #'clojure.core/into-array,
    :meta
    {:added "1.0",
     :ns
     ^{:doc "Fundamental library of the Clojure language",
       :author "Rich Hickey"}
     #object[clojure.lang.Namespace 0x4f629aa4 "clojure.core"],
     :name into-array,
     :file "clojure/core.clj",
     :static true,
     :column 1,
     :line 3443,
     :arglists ([aseq] [type aseq]),
     :doc
     "Returns an array with components set to the values in aseq. The array's\n  component type is type if provided, or the type of the first value in\n  aseq if present, or Object. All values in aseq must be compatible with\n  the component type. Class objects for the primitive types can be obtained\n  using, e.g., Integer/TYPE."},
    :arglists ([aseq] [type aseq]),
    :assignable? false,
    :o-tag java.lang.Object},
   :args
   [{:op :const,
     :eastwood/path
     [1 :init :expr :methods 0 :body :statements 0 :args 2 :args 0],
     :tag java.lang.Class,
     :form ^{:line 7} OpenOption,
     :val java.nio.file.OpenOption,
     :literal? true,
     :o-tag java.lang.Class,
     :type :class}
    {:op :with-meta,
     :children [:meta :expr],
     :eastwood/path
     [1 :init :expr :methods 0 :body :statements 0 :args 2 :args 1],
     :tag clojure.lang.PersistentVector,
     :form ^{:line 7} [],
     :meta
     {:op :const,
      :eastwood/path
      [1
       :init
       :expr
       :methods
       0
       :body
       :statements
       0
       :args
       2
       :args
       1
       :meta],
      :tag clojure.lang.PersistentArrayMap,
      :form
      {:file "eastwood/foo.clj",
       :line 7,
       :column 60,
       :end-line 7,
       :end-column 62},
      :val
      {:file "eastwood/foo.clj",
       :line 7,
       :column 60,
       :end-line 7,
       :end-column 62},
      :literal? true,
      :o-tag clojure.lang.PersistentArrayMap,
      :type :map},
     :expr
     {:op :vector,
      :children [:items],
      :eastwood/path
      [1
       :init
       :expr
       :methods
       0
       :body
       :statements
       0
       :args
       2
       :args
       1
       :expr],
      :tag clojure.lang.PersistentVector,
      :form ^{:line 7} [],
      :items [],
      :o-tag clojure.lang.PersistentVector},
     :o-tag java.lang.Object}],
   :meta
   {:file "eastwood/foo.clj",
    :line 7,
    :column 37,
    :end-line 7,
    :end-column 63},
   :o-tag java.lang.Object}],
 :method write,
 :o-tag java.lang.Object}
== Linting done in 911 ms ==
== Warnings: 0 (not including reflection warnings)  Exceptions thrown: 0

...Exceptions thrown: 0 indicates that merely something was printlned, but not exceptions/warnings happened

---

Adding the type hint, the println is gone, but as you say, a new warning shows up:

$ lein eastwood "{:namespaces [eastwood.foo]}"
== Eastwood 0.3.14 Clojure 1.10.1 JVM 1.8.0_281 ==
Directories scanned for source files:


== Linting eastwood.foo ==
src/eastwood/foo.clj:7:3: Reflection warning - call to static method write on java.nio.file.Files can't be resolved (argument types: java.nio.file.Path, [B, unknown).
src/eastwood/foo.clj:7:3: unused-ret-vals: Should use return value of static method call, but it is discarded: (. java.nio.file.Files (write path (byte-array 10) (into-array OpenOption [])))
== Linting done in 693 ms ==
== Warnings: 1 (not including reflection warnings)  Exceptions thrown: 0
~/eastwood (210--unused-defrecord*) $ ~/bin/lein-latest eastwood "{:namespaces [eastwood.foo]}"
== Eastwood 0.3.14 Clojure 1.10.1 JVM 1.8.0_281 ==
Directories scanned for source files:


== Linting eastwood.foo ==
src/eastwood/foo.clj:7:3: Reflection warning - call to static method write on java.nio.file.Files can't be resolved (argument types: java.nio.file.Path, [B, unknown).
== Linting done in 673 ms ==
== Warnings: 0 (not including reflection warnings)  Exceptions thrown: 0

---

My tentative analysis is:

• the println is something that should be fixed, and that I will try to fix asap
  • I don't particularly recommend applying a workaround
• The unused-ret-vals warning works as designed
  • I'd say it's meant to foster a more functional style, which isn't always possible in practice
  • personally, I have disabled that specific warning over the years.
  • perhaps we could have a discussion about how to make that warning more useful and less prone to being irrelevant/disabled.
    • (should be discussed in a different ticket, feel free to open it if particularly interested)

Thanks again, hope to have some news soon!