starlark 0.13.0

An implementation of the Starlark language in Rust.
Documentation 
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/*
 * Copyright 2019 The Starlark in Rust Authors.
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

//! Spelling suggestions.

use strsim::levenshtein;

/// Find a suggestion for a typo.
pub(crate) fn did_you_mean<'a>(
    value: &str,
    variants: impl IntoIterator<Item = &'a str>,
) -> Option<&'a str> {
    if value.is_empty() {
        return None;
    }

    let max_dist = if value.len() <= 2 {
        // we don't want to suggest "cd" for "a"
        1
    } else {
        2
    };

    variants
        .into_iter()
        .map(|v| (v, levenshtein(value, v)))
        .filter(|(_, dist)| *dist <= max_dist)
        .min_by_key(|(_v, sim)| *sim)
        .map(|(v, _)| v)
}

#[cfg(test)]
mod tests {
    use crate::errors::did_you_mean::did_you_mean;

    #[test]
    fn prefixes() {
        assert_eq!(
            Some("cxx_library"),
            did_you_mean("cxx_librar", vec!["cxx_library"])
        );
        assert_eq!(
            Some("cxx_library"),
            did_you_mean("cxx_libra", vec!["cxx_library"])
        );
        assert_eq!(None, did_you_mean("cxx_libr", vec!["cxx_library"]));
    }

    #[test]
    fn typos() {
        assert_eq!(
            Some("cxx_library"),
            did_you_mean("cxx_librarx", vec!["cxx_library"])
        );
        assert_eq!(
            Some("cxx_library"),
            did_you_mean("cxx_libraxx", vec!["cxx_library"])
        );
        assert_eq!(None, did_you_mean("cxx_librxxx", vec!["cxx_library"]));
    }

    #[test]
    fn best() {
        assert_eq!(Some("abc"), did_you_mean("abx", vec!["abc", "abcd"]));
    }

    #[test]
    fn very_short() {
        assert_eq!(Some("a"), did_you_mean("b", vec!["a"]));
        assert_eq!(Some("ab"), did_you_mean("b", vec!["ab"]));
        assert_eq!(None, did_you_mean("b", vec!["cd"]));

        assert_eq!(None, did_you_mean("bc", vec!["de"]));
    }

    #[test]
    fn earlier_variants_are_more_important() {
        assert_eq!(Some("aaaay"), did_you_mean("aaaax", vec!["aaaay", "aaaaz"]));
        assert_eq!(Some("aaaaz"), did_you_mean("aaaax", vec!["aaaaz", "aaaay"]));
    }
}