From e1a0584936b3aa5ce971e875dec750d2ae937d2e Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Wed, 31 Mar 2021 12:51:11 -0600
Subject: massively upgrade error handling

---
 src/makefile/pattern.rs | 40 +++++++++++++++++-----------------------
 1 file changed, 17 insertions(+), 23 deletions(-)

(limited to 'src/makefile/pattern.rs')

diff --git a/src/makefile/pattern.rs b/src/makefile/pattern.rs
index 733721e..2d5f46c 100644
--- a/src/makefile/pattern.rs
+++ b/src/makefile/pattern.rs
@@ -1,37 +1,31 @@
 use regex::{Captures, Regex};
 
-fn compile_pattern(pattern: &str) -> Regex {
+fn compile_pattern(pattern: &str) -> anyhow::Result<Regex> {
     let mut result = String::new();
     for c in pattern.chars() {
-        match c {
-            // This is a nightmare, because we're escaping for regex syntax before we put
-            // things into result.
-
-            // We don't end with a backslash, so this is an unescaped wildcard.
-            '%' if !result.ends_with(r"\\") => {
-                result.push_str(r"(\w*)");
-            }
-
-            // We end with two backslashes, so this is an escaped backslash and then an
-            // unescaped wildcard.
-            '%' if result.ends_with(r"\\\\") => {
-                result = result.strip_suffix(r"\\\\").unwrap().to_string();
+        if c == '%' {
+            if let Some(real_result) = result.strip_suffix(r"\\\\") {
+                // We end with two backslashes, so this is an escaped backslash and then an
+                // unescaped wildcard.
+                result = real_result.to_string();
                 result.push_str(r"\\(\w*)");
-            }
-
-            // We end with one backslash, so this is an escaped wildcard.
-            '%' if result.ends_with(r"\\") => {
-                result = result.strip_suffix(r"\\").unwrap().to_string();
+            } else if let Some(real_result) = result.strip_suffix(r"\\") {
+                // We end with one backslash, so this is an escaped wildcard.
+                result = real_result.to_string();
                 result.push('%');
+            } else {
+                // We don't end with a backslash, so this is an unescaped wildcard.
+                result.push_str(r"(\w*)");
             }
-            _ => result.push_str(&regex::escape(&c.to_string())),
+        } else {
+            result.push_str(&regex::escape(&c.to_string()));
         }
     }
-    Regex::new(&result).expect("built invalid regex!")
+    Ok(Regex::new(&result)?)
 }
 
-pub(crate) fn r#match<'a>(pattern: &str, text: &'a str) -> Option<Captures<'a>> {
-    compile_pattern(pattern).captures(text)
+pub(crate) fn r#match<'a>(pattern: &str, text: &'a str) -> anyhow::Result<Option<Captures<'a>>> {
+    Ok(compile_pattern(pattern)?.captures(text))
 }
 
 #[cfg(test)]
-- 
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