internal: consolidate build context and unit resolution logic

- Centralize logic for resolving units and selecting the best matching
  build context.
- New helpers MatchingBuildContext, SortedBuildContexts provide a
  consistent, efficient approach to build context selection.
- DocumentationForBuildContext now finds the best match based on
  precdence rules rather than just returning the first match.
- A new getUnitContext helper resolves unit metadata and the best build
  context in a single query.
- GetSymbols and GetUnit are now both optimized to use pre-resolved IDs,
  simplifying their queries and removing redundant joins.
- Replaced redundant matchingDoc functions in fetchdatasource and
  fakedatasource.

Change-Id: I9207d3bfe03404483c816090a0b99666f14a36e3
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/759162
Reviewed-by: Jonathan Amsterdam <jba@google.com>
kokoro-CI: kokoro <noreply+kokoro@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ethan Lee <ethanalee@google.com>

1 files changed, 1 insertions, 5 deletions

diff --git a/internal/fetch/unit.go b/internal/fetch/unit.go
index e0c9c6f3..301d2b7d 100644
--- a/internal/fetch/unit.go
+++ b/internal/fetch/unit.go
@@ -6,7 +6,6 @@ package fetch
 
 import (
 	"path"
-	"sort"
 
 	"golang.org/x/pkgsite/internal"
 	"golang.org/x/pkgsite/internal/licenses"
@@ -45,10 +44,7 @@ func moduleUnit(modulePath string, unitMeta *internal.UnitMeta,
 		for _, d := range unit.Documentation {
 			bcs = append(bcs, internal.BuildContext{GOOS: d.GOOS, GOARCH: d.GOARCH})
 		}
-		sort.Slice(bcs, func(i, j int) bool {
-			return internal.CompareBuildContexts(bcs[i], bcs[j]) < 0
-		})
-		unit.BuildContexts = bcs
+		unit.BuildContexts = internal.SortedBuildContexts(bcs)
 	}
 	return unit
 }