Error stemming in Dutch and Spanish

[mateonunez]

Describe the bug
When using the PorterStemmerNl and PorterStemmerEs, natural module can't resolve the following methods: postlude() and isVowel().

PorterStemmerNl:

 TypeError: Cannot read property 'postlude' of undefined

      51 |   }
      52 |
    > 53 |   return input.map(stemmer.stem);
         |                ^
      54 | }
      55 |

postule() returns the word in lowercase

PorterStemmerEs:

    TypeError: Cannot read property 'isVowel' of undefined

      51 |   }
      52 |
    > 53 |   return input.map(stemmer.stem);
         |                ^
      54 | }
      55 |

To Reproduce
Steps to reproduce the behavior:

1. Create a new test
2. Add the following code:

PorterStemmerNl:

  it("Should stem correctly in dutch", async () => {
    // some words in dutch
    const input: string[] = ["banken"];

    // the expected output
    const expected = ["bank"];

    const output = stemArray(input, "dutch");

    expect(output).toEqual(expected);
  });

PorterStemmerEs:

  it("Should stem correctly in spanish", async () => {
    // some words in spanish
    const input: string[] = ["avenida"];

    // the expected output
    const expected = ["aven"];

    const output = stemArray(input, "spanish");

    expect(output).toEqual(expected);
  });

Desktop (please complete the following information):

• OS: Windows 11
• Environment: Jest
• Node: v18.6.0
• pnpm: v7.5.1
• Lyra: v0.0.1-beta-10

Possible solution

I was testing some solutions for this issue, and I've found that the error is caused when the stemArray method passes the reference of the stem method to the input.map()

return input.map(stemmer.stem);

Fixing typos, and extending the map to force the execution of stem method, the stem method works as expected.

I've published a repo with the possible solution and the stemmer tests.

[micheleriva]

Thank you so much for the report, I'll look into that!