Argon

Argon measures your code's cyclomatic complexity.

Installing

Simple as stack install argon or cabal install argon. Note: if you are using Stack and your resolver if too old, you might have to add some packages to your stack.yaml file.

GHC compatibility

Argon is compatible with GHC version 8.0.2 and above. In the releases page you can find binaries for older versions of argon which support GHC versions 7.8 and 7.10.

About the complexity being measured

argon will compute the cyclomatic complexity of Haskell functions, which is the number of decisions in a block of code plus 1. For instance the following function:

func n = case n of
           2 -> 3
           4 -> 6
           _ -> 42

has a cyclomatic complexity of 3.

The boolean operators && and || also affect the this number. For instance the following function:

g n = n < 68 && n `mod` 3 == 2 && n > 49

has a cyclomatic complexity of 3.

As a last example, the following function:

func n = case n of
           2 -> 3
           4 -> 6
           _ -> if 0 < n
                then 7
                else 8

has a cyclomatic complexity of 5.

Cyclomatic complexity provides a very shallow metric of code complexity: a high cyclomatic complexity number does not necessarily mean that the function is complex, and conversely, a low number does not necessarily indicate that the function is simple. However, this number it can be useful for highlighting potential maintainability issues.

Running

The Argon executable expects a list of file paths (files or directories):

$ argon --no-color --min 2 src
src/Argon/Types.hs
    61:5 toJSON - 2
src/Argon/Visitor.hs
    55:1 visitExp - 5
    62:1 visitOp - 4
    28:11 visit - 2
    35:1 getFuncName - 2
src/Argon/Parser.hs
    55:1 parseModuleWithCpp - 3
    88:1 customLogAction - 3
    35:1 analyze - 2
    39:9 analysis - 2
src/Argon/Formatters.hs
    61:1 formatResult - 3
    42:1 coloredFunc - 2
    43:11 color - 2
src/Argon/Results.hs
    35:1 export - 3
    28:1 filterResults - 2
src/Argon/Loc.hs
    18:11 toRealSrcLoc - 2

For every file, Argon sorts results with the following criteria (and in this order):

1. complexity (descending)
2. line number (ascending)
3. alphabetically

When colors are enabled (default), Argon computes a rank associated with the complexity score:

JSON

Results can also be exported to JSON:

$ argon --json --min 2 src
[
  { "blocks": [ ], "path": "src/Argon.hs", "type": "result" },
  {
    "blocks": [{ "complexity": 2, "name": "toJSON", "lineno": 61, "col": 5 }],
    "path": "src/Argon/Types.hs",
    "type": "result"
  },
  {
    "blocks": [
      { "complexity": 5, "name": "visitExp", "lineno": 55, "col": 1 },
      { "complexity": 4, "name": "visitOp", "lineno": 62, "col": 1 },
      { "complexity": 2, "name": "visit", "lineno": 28, "col": 11 },
      { "complexity": 2, "name": "getFuncName", "lineno": 35, "col": 1 }
    ],
    "path": "src/Argon/Visitor.hs",
    "type": "result"
  },
  {
    "blocks": [
      { "complexity": 3, "name": "parseModuleWithCpp", "lineno": 55, "col": 1 },
      { "complexity": 3, "name": "customLogAction", "lineno": 88, "col": 1 },
      { "complexity": 2, "name": "analyze", "lineno": 35, "col": 1 },
      { "complexity": 2, "name": "analysis", "lineno": 39, "col": 9 }
    ],
    "path": "src/Argon/Parser.hs",
    "type": "result"
  },
  {
    "blocks": [
      { "complexity": 3, "name": "formatResult", "lineno": 61, "col": 1 },
      { "complexity": 2, "name": "coloredFunc", "lineno": 42, "col": 1 },
      { "complexity": 2, "name": "color", "lineno": 43, "col": 11 }
    ],
    "path": "src/Argon/Formatters.hs",
    "type": "result"
  },
  {
    "blocks": [
      { "complexity": 3, "name": "export", "lineno": 35, "col": 1 },
      { "complexity": 2, "name": "filterResults", "lineno": 28, "col": 1 }
    ],
    "path": "src/Argon/Results.hs",
    "type": "result"
  },
  {
    "blocks": [{ "complexity": 2, "name": "toRealSrcLoc", "lineno": 18, "col": 11 }],
    "path": "src/Argon/Loc.hs",
    "type": "result"
  },
  { "blocks": [ ], "path": "src/Argon/Preprocess.hs", "type": "result" }
]