go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/analysis/internal/clustering/rules/lang/merge.go (about)

     1  // Copyright 2022 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package lang
    16  
    17  import (
    18  	"bytes"
    19  	"sort"
    20  	"strings"
    21  )
    22  
    23  // Merge merges two failure association rules with a logical "OR".
    24  func Merge(rule1 string, rule2 string) (string, error) {
    25  	r1, err := Parse(rule1)
    26  	if err != nil {
    27  		return "", err
    28  	}
    29  	r2, err := Parse(rule2)
    30  	if err != nil {
    31  		return "", err
    32  	}
    33  	// The final "OR" conjoined terms.
    34  	var allTerms []*boolTerm
    35  	allTerms = append(allTerms, r1.expr.Terms...)
    36  	allTerms = append(allTerms, r2.expr.Terms...)
    37  
    38  	// Sort the top-level OR'ed terms.
    39  	// A common case we see is a list of tests:
    40  	// test = "mytest://a" OR
    41  	// test = "mytest://b" ...
    42  	// and having the terms sorted makes it easier to
    43  	// read the rule.
    44  	var stringTerms []string
    45  	for _, term := range allTerms {
    46  		var buf bytes.Buffer
    47  		term.format(&buf)
    48  		stringTerms = append(stringTerms, buf.String())
    49  	}
    50  	sort.Strings(stringTerms)
    51  
    52  	// Note that this is only valid because OR is the operator
    53  	// with the lowest precedence in our language.
    54  	// Otherwise we would have to be concerned about inserting
    55  	// parentheses.
    56  	return strings.Join(stringTerms, " OR\n"), nil
    57  }