i/prompting: implement path pattern matching and validation #13866
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| Original file line number | Diff line number | Diff line change |
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| // -*- Mode: Go; indent-tabs-mode: t -*- | ||
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| /* | ||
| * Copyright (C) 2024 Canonical Ltd | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License version 3 as | ||
| * published by the Free Software Foundation. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
| * | ||
| */ | ||
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| package prompting | ||
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| import ( | ||
| "fmt" | ||
| "strings" | ||
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| doublestar "github.com/bmatcuk/doublestar/v4" | ||
| ) | ||
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| type countStack []int | ||
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| func (c *countStack) push(x int) { | ||
| *c = append(*c, x) | ||
| } | ||
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| func (c *countStack) pop() int { | ||
| x := (*c)[len(*c)-1] | ||
| *c = (*c)[:len(*c)-1] | ||
| return x | ||
| } | ||
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| // Limit the number of expanded path patterns for a particular pattern. | ||
| // When fully expanded, the number of patterns for a given unexpanded pattern | ||
| // may not exceed this limit. | ||
| const maxExpandedPatterns = 1000 | ||
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| // ValidatePathPattern returns nil if the pattern is valid, otherwise an error. | ||
| func ValidatePathPattern(pattern string) error { | ||
| if pattern == "" || pattern[0] != '/' { | ||
| return fmt.Errorf("invalid path pattern: must start with '/': %q", pattern) | ||
| } | ||
| depth := 0 | ||
| var currentGroupStack countStack | ||
| var currentOptionStack countStack | ||
| // Final currentOptionCount will be total expanded patterns for full pattern | ||
| currentGroupCount := 0 | ||
| currentOptionCount := 1 | ||
| reader := strings.NewReader(pattern) | ||
| for { | ||
| r, _, err := reader.ReadRune() | ||
| if err != nil { | ||
| // No more runes | ||
| break | ||
| } | ||
| switch r { | ||
| case '{': | ||
| depth++ | ||
| if depth >= maxExpandedPatterns { | ||
| return fmt.Errorf("invalid path pattern: nested group depth exceeded maximum number of expanded path patterns (%d): %q", maxExpandedPatterns, pattern) | ||
| } | ||
| currentGroupStack.push(currentGroupCount) | ||
| currentOptionStack.push(currentOptionCount) | ||
| currentGroupCount = 0 | ||
| currentOptionCount = 1 | ||
| case ',': | ||
| if depth == 0 { | ||
| // Ignore commas outside of groups | ||
| break | ||
| } | ||
| currentGroupCount += currentOptionCount | ||
| currentOptionCount = 1 | ||
| case '}': | ||
| depth-- | ||
| if depth < 0 { | ||
| return fmt.Errorf("invalid path pattern: unmatched '}' character: %q", pattern) | ||
| } | ||
| currentGroupCount += currentOptionCount | ||
| currentOptionCount = currentOptionStack.pop() // option count of parent | ||
| currentOptionCount *= currentGroupCount // parent option count * current group count | ||
| currentGroupCount = currentGroupStack.pop() // group count of parent | ||
| case '\\': | ||
| // Skip next rune | ||
| _, _, err = reader.ReadRune() | ||
|
There was a problem hiding this comment. isn't the escape sequence valid only for some of the characters that follow? eg what would a pattern like There was a problem hiding this comment. According to |
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| if err != nil { | ||
| return fmt.Errorf(`invalid path pattern: trailing unescaped '\' character: %q`, pattern) | ||
| } | ||
| case '[', ']': | ||
| return fmt.Errorf("invalid path pattern: cannot contain unescaped '[' or ']': %q", pattern) | ||
| } | ||
| } | ||
| if depth != 0 { | ||
| return fmt.Errorf("invalid path pattern: unmatched '{' character: %q", pattern) | ||
| } | ||
| if currentOptionCount > maxExpandedPatterns { | ||
| return fmt.Errorf("invalid path pattern: exceeded maximum number of expanded path patterns (%d): %q expands to %d patterns", maxExpandedPatterns, pattern, currentOptionCount) | ||
| } | ||
| if !doublestar.ValidatePattern(pattern) { | ||
| return fmt.Errorf("invalid path pattern: %q", pattern) | ||
| } | ||
| return nil | ||
| } | ||
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| // PathPatternMatch returns true if the given pattern matches the given path. | ||
| // | ||
| // The pattern should not contain groups, and should likely have been an output | ||
| // of ExpandPathPattern. | ||
| // | ||
| // Paths to directories are received with trailing slashes, but we don't want | ||
| // to require the user to include a trailing '/' if they want to match | ||
| // directories (and end their pattern with `{,/}` if they want to match both | ||
| // directories and non-directories). Thus, we want to ensure that patterns | ||
| // without trailing slashes match paths with trailing slashes. However, | ||
| // patterns with trailing slashes should not match paths without trailing | ||
| // slashes. | ||
| // | ||
| // The doublestar package has special cases for patterns ending in `/**` and | ||
| // `/**/`: `/foo/**`, and `/foo/**/` both match `/foo` and `/foo/`. We want to | ||
| // override this behavior to make `/foo/**/` not match `/foo`. We also want to | ||
| // override doublestar to make `/foo` match `/foo/`. | ||
| func PathPatternMatch(pattern string, path string) (bool, error) { | ||
| // Check the usual doublestar match first, in case the pattern is malformed | ||
| // and causes an error, and return the error if so. | ||
| matched, err := doublestar.Match(pattern, path) | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
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There was a problem hiding this comment. wouldn't the pattern be validated prior to being used? Perhaps ValidatePathPatter should call doublestar.Match with say "/" as path, discard the result and only check the error? There was a problem hiding this comment.
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| // No matter if doublestar matched, return false if pattern ends in '/' but | ||
| // path is not a directory. | ||
| if strings.HasSuffix(pattern, "/") && !strings.HasSuffix(path, "/") { | ||
| return false, nil | ||
| } | ||
| if matched { | ||
| return true, nil | ||
| } | ||
| if strings.HasSuffix(pattern, "/") { | ||
| return false, nil | ||
| } | ||
| // Try again with a '/' appended to the pattern, so patterns like `/foo` | ||
| // match paths like `/foo/`. | ||
| return doublestar.Match(pattern+"/", path) | ||
| } | ||
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I think I'm confused even more now. The spec does not mention
{}for path patterns, so why validate this? Also, there's inconsistency between ValidatePathPattern and MatchPathPatter, where the latter is oblivious to{}, which means that a definition of a valid pattern is different for each of those calls.There was a problem hiding this comment.
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MatchPathPatterndirectly callsdoublestar.Matchto do matching (discussed some here: https://docs.google.com/document/d/1tBnefdukP69EUJOlH8bgD2hrvZCYoE8-1ZlqRRYlOqc/edit?pli=1#heading=h.a0e0vfqho1ip). This should be called on expanded patterns, but this isn't technically necessary, sincedoublestar.Matchhappily matches patterns with'{''}'groups in them (see: https://pkg.go.dev/github.com/bmatcuk/doublestar#Match). Path pattern validation should occur on patterns before they are expanded, so they may contain'{''}'-defined groups.