internal/lsp/tests: simplify comparison of markdown at go1.18

In several places throughout the x/tools codebase, the internal/lsp/diff
package is used to provide clearer test output when comparing large,
multi-line strings. In some places, this is implemented via the
tests.Diff helper function, but in others it is not (presumably due to
import cycles).

Factor out this pattern into a diff.Pretty function, and add commentary.
Also remove the *testing.T argument, as diffs should never fail; opt to
panic instead. Also add a test.

Using this function, simplify the logic to comparing our 1.18 markdown
output with 1.19 golden content, by normalizing differences between the
two.

This is necessary as markdown content will change as a result of moving
internal/lsp to gopls/internal/lsp.

For golang/go#54509

Change-Id: Ie1fea1091bbbeb49e00c4efa7e02707cafa415cc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/426776
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

gopls/internal/regtest/codelens/codelens_test.go

@@ -11,10 +11,10 @@ import (
 	"golang.org/x/tools/gopls/internal/hooks"
 	"golang.org/x/tools/internal/lsp/bug"
 	. "golang.org/x/tools/internal/lsp/regtest"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 
 	"golang.org/x/tools/internal/lsp/command"
 	"golang.org/x/tools/internal/lsp/protocol"
-	"golang.org/x/tools/internal/lsp/tests"
 	"golang.org/x/tools/internal/testenv"
 )
 
@@ -187,10 +187,10 @@ require golang.org/x/hello v1.2.3
 				}
 				env.Await(env.DoneWithChangeWatchedFiles())
 				if got := env.Editor.BufferText("a/go.mod"); got != wantGoModA {
-					t.Fatalf("a/go.mod upgrade failed:\n%s", tests.Diff(t, wantGoModA, got))
+					t.Fatalf("a/go.mod upgrade failed:\n%s", compare.Text(wantGoModA, got))
 				}
 				if got := env.Editor.BufferText("b/go.mod"); got != wantGoModB {
-					t.Fatalf("b/go.mod changed unexpectedly:\n%s", tests.Diff(t, wantGoModB, got))
+					t.Fatalf("b/go.mod changed unexpectedly:\n%s", compare.Text(wantGoModB, got))
 				}
 			})
 		})
@@ -220,10 +220,10 @@ require golang.org/x/hello v1.2.3
 				env.ApplyQuickFixes("a/go.mod", d.Diagnostics)
 				env.Await(env.DoneWithChangeWatchedFiles())
 				if got := env.Editor.BufferText("a/go.mod"); got != wantGoModA {
-					t.Fatalf("a/go.mod upgrade failed:\n%s", tests.Diff(t, wantGoModA, got))
+					t.Fatalf("a/go.mod upgrade failed:\n%s", compare.Text(wantGoModA, got))
 				}
 				if got := env.Editor.BufferText("b/go.mod"); got != wantGoModB {
-					t.Fatalf("b/go.mod changed unexpectedly:\n%s", tests.Diff(t, wantGoModB, got))
+					t.Fatalf("b/go.mod changed unexpectedly:\n%s", compare.Text(wantGoModB, got))
 				}
 			})
 		})
@@ -285,7 +285,7 @@ go 1.14
 require golang.org/x/hello v1.0.0
 `
 		if got != wantGoMod {
-			t.Fatalf("go.mod tidy failed:\n%s", tests.Diff(t, wantGoMod, got))
+			t.Fatalf("go.mod tidy failed:\n%s", compare.Text(wantGoMod, got))
 		}
 	})
 }

gopls/internal/regtest/misc/definition_test.go

@@ -11,10 +11,10 @@ import (
 
 	"golang.org/x/tools/internal/lsp/protocol"
 	. "golang.org/x/tools/internal/lsp/regtest"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 	"golang.org/x/tools/internal/testenv"
 
 	"golang.org/x/tools/internal/lsp/fake"
-	"golang.org/x/tools/internal/lsp/tests"
 )
 
 const internalDefinition = `
@@ -133,7 +133,7 @@ func main() {
 		}
 		want := "```go\nfunc (error).Error() string\n```"
 		if content.Value != want {
-			t.Fatalf("hover failed:\n%s", tests.Diff(t, want, content.Value))
+			t.Fatalf("hover failed:\n%s", compare.Text(want, content.Value))
 		}
 	})
 }

gopls/internal/regtest/misc/fix_test.go

@@ -8,9 +8,9 @@ import (
 	"testing"
 
 	. "golang.org/x/tools/internal/lsp/regtest"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 
 	"golang.org/x/tools/internal/lsp/protocol"
-	"golang.org/x/tools/internal/lsp/tests"
 )
 
 // A basic test for fillstruct, now that it uses a command.
@@ -56,7 +56,7 @@ func Foo() {
 }
 `
 		if got := env.Editor.BufferText("main.go"); got != want {
-			t.Fatalf("TestFillStruct failed:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("TestFillStruct failed:\n%s", compare.Text(want, got))
 		}
 	})
 }

gopls/internal/regtest/misc/formatting_test.go

@@ -9,8 +9,7 @@ import (
 	"testing"
 
 	. "golang.org/x/tools/internal/lsp/regtest"
-
-	"golang.org/x/tools/internal/lsp/tests"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 )
 
 const unformattedProgram = `
@@ -37,7 +36,7 @@ func TestFormatting(t *testing.T) {
 		got := env.Editor.BufferText("main.go")
 		want := env.ReadWorkspaceFile("main.go.golden")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -59,7 +58,7 @@ func f() {}
 		got := env.Editor.BufferText("a.go")
 		want := env.ReadWorkspaceFile("a.go.formatted")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -83,7 +82,7 @@ func f() { fmt.Println() }
 		got := env.Editor.BufferText("a.go")
 		want := env.ReadWorkspaceFile("a.go.imported")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -104,7 +103,7 @@ func f() {}
 		got := env.Editor.BufferText("a.go")
 		want := env.ReadWorkspaceFile("a.go.imported")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -150,7 +149,7 @@ func TestOrganizeImports(t *testing.T) {
 		got := env.Editor.BufferText("main.go")
 		want := env.ReadWorkspaceFile("main.go.organized")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -162,7 +161,7 @@ func TestFormattingOnSave(t *testing.T) {
 		got := env.Editor.BufferText("main.go")
 		want := env.ReadWorkspaceFile("main.go.formatted")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -262,7 +261,7 @@ func main() {
 				got := env.Editor.BufferText("main.go")
 				got = strings.ReplaceAll(got, "\r\n", "\n") // convert everything to LF for simplicity
 				if tt.want != got {
-					t.Errorf("unexpected content after save:\n%s", tests.Diff(t, tt.want, got))
+					t.Errorf("unexpected content after save:\n%s", compare.Text(tt.want, got))
 				}
 			})
 		})
@@ -361,7 +360,7 @@ const Bar = 42
 		got := env.Editor.BufferText("foo.go")
 		want := env.ReadWorkspaceFile("foo.go.formatted")
 		if got != want {
-			t.Errorf("unexpected formatting result:\n%s", tests.Diff(t, want, got))
+			t.Errorf("unexpected formatting result:\n%s", compare.Text(want, got))
 		}
 	})
 }

gopls/internal/regtest/misc/import_test.go

@@ -11,7 +11,7 @@ import (
 	"golang.org/x/tools/internal/lsp/command"
 	"golang.org/x/tools/internal/lsp/protocol"
 	. "golang.org/x/tools/internal/lsp/regtest"
-	"golang.org/x/tools/internal/lsp/tests"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 )
 
 func TestAddImport(t *testing.T) {
@@ -51,7 +51,7 @@ func main() {
 		}, nil)
 		got := env.Editor.BufferText("main.go")
 		if got != want {
-			t.Fatalf("gopls.add_import failed\n%s", tests.Diff(t, want, got))
+			t.Fatalf("gopls.add_import failed\n%s", compare.Text(want, got))
 		}
 	})
 }

gopls/internal/regtest/modfile/modfile_test.go

@@ -13,9 +13,9 @@ import (
 	"golang.org/x/tools/gopls/internal/hooks"
 	"golang.org/x/tools/internal/lsp/bug"
 	. "golang.org/x/tools/internal/lsp/regtest"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 
 	"golang.org/x/tools/internal/lsp/protocol"
-	"golang.org/x/tools/internal/lsp/tests"
 	"golang.org/x/tools/internal/testenv"
 )
 
@@ -101,7 +101,7 @@ func main() {
 				),
 			)
 			if got := env.ReadWorkspaceFile("a/go.mod"); got != goModContent {
-				t.Fatalf("go.mod changed on disk:\n%s", tests.Diff(t, goModContent, got))
+				t.Fatalf("go.mod changed on disk:\n%s", compare.Text(goModContent, got))
 			}
 			// Save the buffer, which will format and organize imports.
 			// Confirm that the go.mod file still does not change.
@@ -110,7 +110,7 @@ func main() {
 				env.DiagnosticAtRegexp("a/main.go", "\"example.com/blah\""),
 			)
 			if got := env.ReadWorkspaceFile("a/go.mod"); got != goModContent {
-				t.Fatalf("go.mod changed on disk:\n%s", tests.Diff(t, goModContent, got))
+				t.Fatalf("go.mod changed on disk:\n%s", compare.Text(goModContent, got))
 			}
 		})
 	})
@@ -154,7 +154,7 @@ func main() {
 				),
 			)
 			if got := env.ReadWorkspaceFile("a/go.mod"); got != goModContent {
-				t.Fatalf("go.mod changed on disk:\n%s", tests.Diff(t, goModContent, got))
+				t.Fatalf("go.mod changed on disk:\n%s", compare.Text(goModContent, got))
 			}
 		})
 	})
@@ -206,7 +206,7 @@ require example.com v1.2.3
 		}
 		env.ApplyQuickFixes("a/main.go", []protocol.Diagnostic{goGetDiag})
 		if got := env.ReadWorkspaceFile("a/go.mod"); got != want {
-			t.Fatalf("unexpected go.mod content:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("unexpected go.mod content:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -256,7 +256,7 @@ require random.org v1.2.3
 		}
 		env.ApplyQuickFixes("a/main.go", []protocol.Diagnostic{randomDiag})
 		if got := env.ReadWorkspaceFile("a/go.mod"); got != want {
-			t.Fatalf("unexpected go.mod content:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("unexpected go.mod content:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -312,7 +312,7 @@ require random.org v1.2.3
 		}
 		env.ApplyQuickFixes("a/main.go", []protocol.Diagnostic{randomDiag})
 		if got := env.ReadWorkspaceFile("a/go.mod"); got != want {
-			t.Fatalf("unexpected go.mod content:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("unexpected go.mod content:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -359,7 +359,7 @@ require example.com v1.2.3
 		)
 		env.ApplyQuickFixes("a/go.mod", d.Diagnostics)
 		if got := env.Editor.BufferText("a/go.mod"); got != want {
-			t.Fatalf("unexpected go.mod content:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("unexpected go.mod content:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -404,7 +404,7 @@ go 1.14
 		)
 		env.ApplyQuickFixes("a/go.mod", d.Diagnostics)
 		if got := env.Editor.BufferText("a/go.mod"); got != want {
-			t.Fatalf("unexpected go.mod content:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("unexpected go.mod content:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -476,7 +476,7 @@ require (
 )
 `
 		if got := env.ReadWorkspaceFile("a/go.mod"); got != want {
-			t.Fatalf("TestNewDepWithUnusedDep failed:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("TestNewDepWithUnusedDep failed:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -585,7 +585,7 @@ require (
 		env.SaveBuffer("a/go.mod")
 		env.Await(EmptyDiagnostics("a/main.go"))
 		if got := env.Editor.BufferText("a/go.mod"); got != want {
-			t.Fatalf("suggested fixes failed:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("suggested fixes failed:\n%s", compare.Text(want, got))
 		}
 	})
 }
@@ -773,7 +773,7 @@ func main() {
 		)
 		got := env.ReadWorkspaceFile("go.mod")
 		if got != original {
-			t.Fatalf("go.mod file modified:\n%s", tests.Diff(t, original, got))
+			t.Fatalf("go.mod file modified:\n%s", compare.Text(original, got))
 		}
 		env.RunGoCommand("get", "example.com/blah@v1.2.3")
 		env.RunGoCommand("mod", "tidy")
@@ -1026,7 +1026,7 @@ go 1.12
 `
 			env.ApplyQuickFixes("go.mod", d.Diagnostics)
 			if got := env.Editor.BufferText("go.mod"); got != want {
-				t.Fatalf("unexpected content in go.mod:\n%s", tests.Diff(t, want, got))
+				t.Fatalf("unexpected content in go.mod:\n%s", compare.Text(want, got))
 			}
 		})
 	})
@@ -1079,7 +1079,7 @@ require random.com v1.2.3
 			}
 			env.ApplyQuickFixes("go.mod", diagnostics)
 			if got := env.Editor.BufferText("go.mod"); got != want {
-				t.Fatalf("unexpected content in go.mod:\n%s", tests.Diff(t, want, got))
+				t.Fatalf("unexpected content in go.mod:\n%s", compare.Text(want, got))
 			}
 		})
 	})
@@ -1125,7 +1125,7 @@ func main() {
 example.com v1.2.3/go.mod h1:Y2Rc5rVWjWur0h3pd9aEvK5Pof8YKDANh9gHA2Maujo=
 `
 		if got := env.ReadWorkspaceFile("go.sum"); got != want {
-			t.Fatalf("unexpected go.sum contents:\n%s", tests.Diff(t, want, got))
+			t.Fatalf("unexpected go.sum contents:\n%s", compare.Text(want, got))
 		}
 	})
 }

internal/lsp/cmd/test/suggested_fix.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 
 	"golang.org/x/tools/internal/lsp/tests"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -32,6 +33,6 @@ func (r *runner) SuggestedFix(t *testing.T, spn span.Span, suggestedFixes []test
 		return []byte(got), nil
 	}))
 	if want != got {
-		t.Errorf("suggested fixes failed for %s:\n%s", filename, tests.Diff(t, want, got))
+		t.Errorf("suggested fixes failed for %s:\n%s", filename, compare.Text(want, got))
 	}
 }

internal/lsp/cmd/test/workspace_symbol.go

@@ -13,6 +13,7 @@ import (
 
 	"golang.org/x/tools/internal/lsp/source"
 	"golang.org/x/tools/internal/lsp/tests"
+	"golang.org/x/tools/internal/lsp/tests/compare"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -48,6 +49,6 @@ func (r *runner) runWorkspaceSymbols(t *testing.T, uri span.URI, matcher, query
 	}))
 
 	if expect != got {
-		t.Errorf("workspace_symbol failed for %s:\n%s", query, tests.Diff(t, expect, got))
+		t.Errorf("workspace_symbol failed for %s:\n%s", query, compare.Text(expect, got))
 	}
 }