Don't error on multiple matching index URLs (astral-sh#2627)

## Summary

Closes Issue:
- astral-sh#2626

## Test Plan

```
cargo run -- pip install -r dev-requirements.txt -r requirements.txt
```
where both requirements files have same `--index-url`

crates/distribution-types/src/index_url.rs

@@ -28,7 +28,7 @@ pub enum IndexUrl {
 
 impl IndexUrl {
     /// Return the raw URL for the index.
-    pub(crate) fn url(&self) -> &Url {
+    pub fn url(&self) -> &Url {
         match self {
             Self::Pypi(url) => url.raw(),
             Self::Url(url) => url.raw(),

crates/uv-requirements/Cargo.toml

@@ -10,6 +10,7 @@ authors.workspace = true
 license.workspace = true
 
 [dependencies]
+cache-key = { workspace = true }
 distribution-filename = { workspace = true }
 distribution-types = { workspace = true }
 pep508_rs = { workspace = true }

crates/uv-requirements/src/specification.rs

@@ -5,7 +5,7 @@ use indexmap::IndexMap;
 use rustc_hash::FxHashSet;
 use tracing::{instrument, Level};
 
-use crate::{ExtrasSpecification, RequirementsSource};
+use cache_key::CanonicalUrl;
 use distribution_types::{FlatIndexLocation, IndexUrl};
 use pep508_rs::{Requirement, RequirementsTxtRequirement};
 use requirements_txt::{EditableRequirement, FindLink, RequirementsTxt};
@@ -14,6 +14,8 @@ use uv_fs::Simplified;
 use uv_normalize::{ExtraName, PackageName};
 use uv_warnings::warn_user;
 
+use crate::{ExtrasSpecification, RequirementsSource};
+
 #[derive(Debug, Default)]
 pub struct RequirementsSpecification {
     /// The name of the project specifying requirements.
@@ -205,13 +207,15 @@ impl RequirementsSpecification {
                 spec.project = source.project;
             }
 
-            if let Some(url) = source.index_url {
+            if let Some(index_url) = source.index_url {
                 if let Some(existing) = spec.index_url {
-                    return Err(anyhow::anyhow!(
-                        "Multiple index URLs specified: `{existing}` vs.` {url}",
-                    ));
+                    if CanonicalUrl::new(index_url.url()) != CanonicalUrl::new(existing.url()) {
+                        return Err(anyhow::anyhow!(
+                            "Multiple index URLs specified: `{existing}` vs. `{index_url}`",
+                        ));
+                    }
                 }
-                spec.index_url = Some(url);
+                spec.index_url = Some(index_url);
             }
             spec.no_index |= source.no_index;
             spec.extra_index_urls.extend(source.extra_index_urls);
@@ -236,13 +240,15 @@ impl RequirementsSpecification {
             spec.constraints.extend(source.constraints);
             spec.constraints.extend(source.overrides);
 
-            if let Some(url) = source.index_url {
+            if let Some(index_url) = source.index_url {
                 if let Some(existing) = spec.index_url {
-                    return Err(anyhow::anyhow!(
-                        "Multiple index URLs specified: `{existing}` vs.` {url}",
-                    ));
+                    if CanonicalUrl::new(index_url.url()) != CanonicalUrl::new(existing.url()) {
+                        return Err(anyhow::anyhow!(
+                            "Multiple index URLs specified: `{existing}` vs. `{index_url}`",
+                        ));
+                    }
                 }
-                spec.index_url = Some(url);
+                spec.index_url = Some(index_url);
             }
             spec.no_index |= source.no_index;
             spec.extra_index_urls.extend(source.extra_index_urls);
@@ -267,13 +273,15 @@ impl RequirementsSpecification {
             spec.overrides.extend(source.constraints);
             spec.overrides.extend(source.overrides);
 
-            if let Some(url) = source.index_url {
+            if let Some(index_url) = source.index_url {
                 if let Some(existing) = spec.index_url {
-                    return Err(anyhow::anyhow!(
-                        "Multiple index URLs specified: `{existing}` vs.` {url}",
-                    ));
+                    if CanonicalUrl::new(index_url.url()) != CanonicalUrl::new(existing.url()) {
+                        return Err(anyhow::anyhow!(
+                            "Multiple index URLs specified: `{existing}` vs. `{index_url}`",
+                        ));
+                    }
                 }
-                spec.index_url = Some(url);
+                spec.index_url = Some(index_url);
             }
             spec.no_index |= source.no_index;
             spec.extra_index_urls.extend(source.extra_index_urls);

crates/uv/tests/pip_compile.rs

@@ -3812,7 +3812,7 @@ fn index_url_requirements_txt() -> Result<()> {
     Ok(())
 }
 
-/// Raise an error when multiple `requirements.txt` files include `--index-url` flags.
+/// Raise an error when multiple `requirements.txt` files include different `--index-url` flags.
 #[test]
 fn conflicting_index_urls_requirements_txt() -> Result<()> {
     let context = TestContext::new("3.12");
@@ -3831,7 +3831,35 @@ fn conflicting_index_urls_requirements_txt() -> Result<()> {
     ----- stdout -----
 
     ----- stderr -----
-    error: Multiple index URLs specified: `https://google.com/` vs.` https://wikipedia.org/
+    error: Multiple index URLs specified: `https://google.com/` vs. `https://wikipedia.org/`
+    "###
+    );
+
+    Ok(())
+}
+
+/// Doesn't raise an error when multiple `requirements.txt` files include matching `--index-url` flags.
+#[test]
+fn matching_index_urls_requirements_txt() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("--index-url https://pypi.org/simple")?;
+
+    let constraints_in = context.temp_dir.child("constraints.in");
+    constraints_in.write_str("--index-url https://pypi.org/simple")?;
+
+    uv_snapshot!(context.compile()
+            .arg("requirements.in")
+            .arg("--constraint")
+            .arg("constraints.in"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] --exclude-newer 2023-11-18T12:00:00Z requirements.in --constraint constraints.in
+
+    ----- stderr -----
+    Resolved 0 packages in [TIME]
     "###
     );